It's been known for a few months that a new radio production of the Hitchhiker's Guide to the Galaxy has been in the works. In fact, the production company contracted by the BBC to do so had already recorded the adaptation of Life, the Universe, and Everything and were all set to air it on the radio this past winter...until they ran into a problem.....
The movie version IS FILMING, RIGHT NOW, and there were some messy rights issues involved, but they apparently have cleared them with all parties, as
21 September 2004
marks the return to BBC4 (and yes, it should be listenable on the Internet, via RealPlayer).

http://www.bbc.co.uk/radio4/hitchhikers/index.shtml

This also means they can finally get underway with the adaptations of books 4 and 5....

[edit: For the record, it looks like the BBC Cult site (www.bbc.co.uk/cult) posted this news on Monday the 21st, but I've been a little behind in reading my "usual websites"]