XMMS now has a CVS server (thanks to Falsehope) from where you can download the latest development version. It's rather easy to use CVS, first of all if your system lacks CVS, download it from http://www.loria.fr/~molli/cvs-index.html. Once you've made sure that CVS is on your system you have to set an enviroment variable:

for bash:
export CVSROOT=":pserver:anonymous@cvs.xmms.org:/cvs"

for csh:
setenv CVSROOT ":pserver:anonymous@cvs.xmms.org:/cvs"

When you have set the variable use cvs login to login to the CVS server. (just hit enter when it asks for the password) cd to the dir where you want the XMMS source to be downloaded to, then run

cvs -z3 checkout xmms
Please use the -z3 option to minimize network bandwidth (-z9 eats too much CPU time - please don't use it).

Once the checkout is completed, cd xmms/ and then ./autogen.sh to create the configure script. Once autogen is completed run make and make install to compile and install XMMS.

If you want to update your source tree with the latest changes simply use cvs -z3 update -Pd xmms and do as described above.

Get rpm's of the CVS at Freshmeat

Or at Falsehope that also have a tar ball of the CVS