I think it's important to go to the festival with a reasonable understanding of what most of the bands are like - I went a bit blind last year, and whilst it was still amazing, I missed some bands that I would have died to hear with hindsight - elbow for example! So, as soon as the line-up is announced I will pull together a DVD and CD with music for us to listen to before the festival.

Check back here soon! The rumour is line-up will be out end of May / beginning of June.
In the meantime, how about using Spotify with a Glastonbury playlist which has been put together (install Spotify first). Spotify is a bit of software which streams music off the internet for free - think iTunes with every song ever invented, for free! The Glasto Rumour playlist is maintained by a chap called robith on the eFestivals board, and various tunes from all the rumoured bands are on there to be listened to.. I strongly recommend it!