The release process is overseen by our release manager Stephan Arts. If you want to step in and help with preparing parts of the releases don't hesitate to contact him.
Release process:
Send mail to xfce4-dev@xfce.org mailing-list 2 days before tagging.
NEWS files
Make sure the application actually compiles and that 'make distcheck' works; commit build fixes as needed
Update ChangeLogs (only for module maintainers who use svn2cl)
Bump version numbers (drop 'svn' tag)
Rebuild po/*.po to update Project-Id-Version and prevent problems during make distcheck.
Tag the release in svn
Make release packages
Generate MD5 and SHA1 checksums, and GPG signatures for each module
Upload tarballs (only tar.bz2) to main server (request mirror maintainers to do a manual sync) and Sourceforge
Release announcements/websites:
After the release:
Celebrate
(For stable releases) Update the csm misquote in #xfce-dev
(Possibly a lot more I can't think of right now)