As there is no CentoOS5 repo out there that I know of that ships the latest mono releases, I've setup a yum repository with CentOS 5 mono builds (x86_64 arch only). Not all mono components are there yet, right now I'm only building the ones I need: libgdiplus, mono, xsp and mod_mono (nant is also included).
The packages are built without any extra repository dependency, so should work on stock (fully updated) CentOS5 installs and maybe RHEL5, but I haven't tried. The repository will have the last two stable releases and will track fedora's devel specs and patches as much as possible.
I'm using the builds for production CentOS5 systems, so they are reasonably tested and you'll get new builds following mono releases. If you find any packaging related issues, feel free to contact me
Instructions: Put the mono.repo file in /etc/yum.repos.d and have fun :)
-- Angel Marin