Updated December 2016
The borders with Libya and Morocco are closed to tourists. Mauritania border not accessible. Crossings to Mali and Niger not attempted for years. That leaves only Tunisia or the sea ports. Unexplained visa delays still occur but there are also hints of tourism creeping back in the south.

Algerian dinar exchange rates. Basically about 100 dinars to a euro. Black market might get you 15%.

Price of fuel
Two star petrol (essence) 23d/litre;
Super 30d+/litre where available (unleaded available in the north)
Diesel 13.7 d/litre.

Fuel is cheap. Meals from 200d, camping from 400d, hotels/rooms from 1000d.

Useful languages
Arabic or French.

Borders with Libya have been closed for years for tourists and as things are now, getting too close to the Libya border is risky.
You can’t cross into Mali (nor would you want to) and crossing into northern Niger via In Guezzam may be tense, if not currently forbidden. You can’t cross directly into Mauritania either – that part of Algeria is a Polisario zone and long time closed. Most overlanders cross and leave from Tunisia via Nefta–Taleb Larbi, or by ferry.

Travellers with vehicles require an agency escort in the desert. Assuming you get a visa, on public transport you might get around freely in the north, but not in the desert. In Salah seems the control point on the TSH beyond which they insist on an agency escort to carry on south. In the Adrar region they may slap a gendarmerie escort on you too, so avoid the road down from Bechar (as we found in 2011). These escorting regs match broadly similar requirements in former Libya and to a lesser extent, travelling in remote parts of Niger and Egypt.

First of all arrange your itinerary (or direct transit to Niger, if possible) with an approved agency (see below), then submit your emailed invite document aka: certificate d’hebergement when applying for a visa. More below.

… of the type encountered in Morocco or Egypt in unknown in Algeria. You will find the people hospitable, courteous or just ‘normal’.
Security is another issue and foreigners are said to be a target. Flying directly into the south for a tour is fine, but driving too close to southern borders (away from the TSH) is unadvisable and may not even be possible. The Tizi Ouzou (Kabylie) region east of Algiers as well as regions bordering northwestern Tunisia are also worth avoiding by tourists. But remember, Algeria is a very big country.

Needed by all citizens of non-Arabic countries, usually must be applied for in your country of residence (which for most people rules out Tunisia or Niger, for example).
In late 2013 your visa application may get turned down if you intend to visit the south which I am told by local agencies is partly closed to foreigners. The Djanet region seems to have reopened, for the fly-in market but in 2015 they wouldn’t even issued visas for here (or to clarify: they took submissions but endlessly delayed issuing visas until it was just too late; an old trick).
The usual path for the Sahara travels was to apply via an agency as described above. For independent travels in the north you can submit a certificate d’hebergment (‘proof of lodging’ – ‘CdH’) by booking a night in a hotel. Finding a hotel that will answer your query and fax the CdH can be another matter. If you have been officially invited to northern Algeria (usually by some institution) a Letter of Introduction with an Algerian address and an explanation is all that is required. In other words travelling around the north without a guide as was possible a few years ago is less easy now but people do manage.
Coming up from West Africa it used to be possible to obtain a regular 30-day visa in Agadez (Niger) the same day for 24,000CFA. The consulate is here (Mon to Fri & Sat morning). But in early 2011 some tried and failed. They also didn’t succeed in Niamey and don’t bank on getting an Alg visa in Bamako, either. Since 2001 Libya has fallen and in Agadez tourists have been replaced by migrants.
Holland requires a hotel booking, a copy of your air ticket, travel insurance and even a bank statement, as well as possibly a confirmation from the travel company you booked with. But in November 2011 this was still not enough to issue a tourist visa.
USA verified Nov 2011 and may contradict info now given on consular website:
We ended up using ABC Visa, which is apparently the same as the Algerian Visa Center. They were very helpful and responsive and they apparently process all Algerian visas coming through any visa agency. We sent them the following items:
• Visa application (2 copies) with passport photos affixed (annotated sample)
• Visa request form (filled out online)
• Postal money order for visa fee ($135 – since increased) and processing fee ($31)
• Invitation letters from Algerian tour agency
• Flight itinerary (round trip from USA to Algeria – we initially just sent from London – Algiers but had to send along our US to London segments, too.
• Passports
•  Return airbill (express mail).
From the time we shipped the works off (using overnight mail) until we got everything back was 8 calendar days, and that was with delays as explained above.”

Belgium things are said to be relaxed, a 30-day visa issued within 5 days for €60 with only a CdH from a hotel and proof of travel insurance.

Algerian Consulate
63 Riding House St, Marylebone, London W1W 7DR (near the BBC)
Apply Mon–Fri 9.30–noon (collection 3–4pm).
Website Read the visa page carefully.

You will need to get on the case weeks before your departure date; firstly by obtaining an invite document from Algeria (lately an emailed pdf is being accepted – one time they insisted on the original copy DHL’d from Algeria), then applying at the consulate and waiting at least a month for your visa.

• Fill out the online visa form here, print off two copies, date and sign both.
• Attach a passport photo to each.
• Make two photocopies of every single double page of your passport, even blank ones.
• Include a letter from your employer, basically saying you work there.
• Proof of travel insurance
• Fee of £85 (or as below).

If not using a visa agency, apply in the basement at the address above between 9.30am and noon, Tues-Fri. Get there early; if you arrive much after 11am you may not get to the head of the queue before they close the door at noon. Downstairs they look over your docs and if they spot any mistakes they will reject or amend. Pay in cash. If all is in order you will be given a receipt with a collection date or they will call you when the passports are ready..
Various contradictory sources state you can only make 1, 2 or 3 applications at a time. If you’re submitting for a group I guess you rejoin the queue and start again. It’s unlikely you could manage more than two runs (2 to 6 passports) on an averagely busy morning at Hyde Park Gate, but as tourist visa apps in person are unusual, they may relent and take up to five at a time.
A single-entry 30-day visa costs £85 for a UK passport holder.
Irish: 7 days £50; 30 days £60; 90-days multi entry £100
Collections are between 3.30 and 40pm Tues-Fri (possibly Sat morning if urgent).

You’re advised not to get a ferry or plane ticket before you secure a visa; and a visa is not guaranteed if they don’t like the cut of your jib. Of course this then means booking a plane or a boat very late. Certainly with a ferry, this can mean that the better exterior cabins can be in short supply. Be warned – so-called promotional ferry tariffs (hardly a bargain) cannot be cancelled or even amended to a future date. With planes, who knows.

Info needed for your invitation
• names and date of birth
• nationality of the participants
• passport numbers
• how are you travelling to Algeria
• registration number of vehicles
• itinerary
• exact dates of entry and exit to the country
• ‘transit’ or a ‘tourist’ visa.

Some tourist agencies in Algeria that I have dealt (or tried to deal) with include:
Agence Ben Kada (Tam – rarely answer emails)
Essendilene Voyages (Djanet)
Timtar Voyages (Tam)
In Ziza (Adrar – email me for contact)

Guide with own car costs about €110-150/day. Guide in your car: €50-70/day.

There are plenty of other agencies of course and about half a dozen good ones. I recently worked with a long-established, Tam based Ben Kada (email available) who were fine on the ground but were very slow to answer emails. A long-established agency. Akar-Akar near Tam seem to charge more than double, and enquiries to ‘Expert Algeria’ soon dried up.

Border formalities – overland
Allow an hour or four from Tunisia at Taleb Larbi (between Nefta – El Oued; the most common entry point where your escort meets you. Fill out police forms for you and your car, then customs declaration forms and maybe get a light search. Then you need to declare and change your official money and buy motor insurance (3000d for 4 weeks for a 4×4). They also do a health briefing (AIDS awareness?). Then you must check into the gendarmerie a couple of kms down the road.
The trans Sahara Highway is now sealed from Algiers all the way to the Niger border at In Guezzam. From there it’s 150km of hard sandy piste to Arlit where the tarmac resumes.

Border formalities: flying in
Into Tam for example, on an organised/private tour: no compulsory exchange required (though you may want to change some anyway for personal use). Just fill out the brown card and possibly a white customs form declaring money and phones, cameras/etc (no binoculars aka: jumelles). This customs sheet is looked at but virtually never checked against your money on the way out. They ask but don’t search much. Arriving in Algiers airport in February 2011 all I did was the brown card – no other forms, no search and no questions about who I was or where I was going.

Desert pistes
The landscapes of south Algeria offer the best of the true Sahara without committing yourself to crossing the desert to West Africa, with clear tracks, many wells and much nomad life.
The Amguid region and track (A9 and A12) as well as A2 and A3 have been said to be closed since the 2003 kidnappings there. Erg Chech is out-of-bounds too; Tassili Hoggar region SE of Tam reopened in 2011 then closed again. It’s all gone too far for tourism as it was to recover  now.
Expect tedious checkpoints in every town and village, some insisting your guide goes to the local barracks to fill out a form; police at every roundabout and checking-in is required with the Gendarmerie if you stop at In Salah and at Tam. A 2009 report on arriving at Algiers from Marseille is here. May 2010 crossing from Niger here and my February 2011 trip report is here,  2012 trip here and 2013 trip here.