ADFS is "Active Directory Federation Services". ADFS is just one part of the R2 release coming at the end of this year. If you want to find out more, one place is IT Forum in Barcelona, November 15th to 17th, with a pre-conference day on 14th November. As well as plenty of breakouts covering all aspects of R2 during the main conference, if you choose to attend the pre-conf day, there is a full days material available dedicated entirely to R2. More information can be found online - click the banner below, and now that we're almost there on wrapping up the final content list, I'll be posting more information up very soon.
However, if you want a step-by-step guide to deploying ADFS using Windows Server 2003 R2 Beta 2 now, take a look at this whitepaper.
I am on the beta testing thing for this and keep on getting R2 chat begins in 2 hours messages and I still haven't actually had time to do anything towards it! Wish I had.