There is a lot of information and resources on R. Much can be found online, through the R help mailing list, online tutorials (see e.g. Quick-R) and of course the R website. There are also numerous blogs. For a start you should check out R bloggers, which aggregates content of over 140 blogs about R.

For the beginner, but probably also for the slightly more advanced user, this post on R Why gives an interesting list with R books for undergraduates. Check it out.