There are several steps for a Libyan visa. You need a lot of cash, photos and forms.

Step 1 - apply for a Letter of Invitation (LoI). I'm not sure where is best to do this - the people funding my trip did this for me. The LoI application involved filling out a form and providing a copy of my passport, plus 2 passport photos. In return you should get an authorisation code. African bureaucracy being what it is, you may not get this code a) on time or b) at all. Hence the fact that I don't have a visa despite needing to fly out there on Wednesday.

Step 2 - get an Arabic translation in your passport. This is a relatively recent requirement as last time I was there I didn't need one. The Arab-British Chamber of Commerce in London can do this for you for a small fee (I think around £25).
See http://www.abcc.org.uk/. It's a handy thing to have in your passport anyway if you travel a lot.

Step 3 - once you have the authorisation code/LoI you take it to the Libyan People's Bureau in London (in Knightsbridge). See http://www.libyan-embassy.co.uk/. You also need 4 more passport photos and yet another application form (downloadable from their website). Like other embassies, it's open very odd
hours. You can only leave in your application on Mon, Tues or Wed between 10am-11am and collect it the following day between 1pm-2pm. You must bring cash to pay for the visa on application. It's £100 per visa.

As for actually entering the country, well it's the usual African bureaucracy I guess - I've only done so by air and had a bunch of research equipment impounded when I flew in and tried to clear customs. Nothing moves quickly in Libya. The roads are okay though. It's an amazing country, so here's hoping I actually get that flight in 72 hours time.