Currently Fedora 10 and Fedora 11 should both work. Fedora 10 will be phased out soon.
To determine which version you are using, just run the following (you may need to install it first, see below for instructions):
A full build using sugar-jhbuild will require about 3 Gig of disk space.
yum install redhat-lsb
Other than that and the packages mentioned by
./sugar-jhbuild depscheck (please see the non-distro specific instructions) nothing else should be required.
If you notice that any package is required, but not mentioned by depscheck, please file a bug report (login required first, but currently no automatic redirection to login page) against the sugar-jhbuild Component on the Sugar Labs bug tracker.