I wanted to drop in and post a link here.  Like some people have said, the Dresden Files RPG will be based on the FATE system.  However, it's a substantially retooled version of the system that's a LOT different from the version of FATE that's available now.  What we're hearing is that the system will basically be the same as that used in Evil Hat's Spirit of the Century RPG, but with a new magic system, and modified damage rules.  SotC is a great pulp game, and I'd recommend buying it if you like pulp.  However, if you're only interested in getting a preview of the rules, you can check out the "system reference document" for SotC here:

http://www.crackmonkey.org/~nick/loyhargil/fate3/fate3.html

(SotC is an "Open Gaming License" product, which means that while setting information and the like is protected, all the system elements may be freely distributed.)

You might also check out the Evil Hat wiki:

http://evilhat.wikidot.com/