One of the most anticipated UT3 features was the possibility of allowing PS3 gamers to import new community content/mods on their consoles. Epic has released an updated version of the tools to "cook" your own content, and transfer it from PC to PS3. This version is up to date for the newest PS3 patch released a few days ago, and requires the v1.2 PC patch installed.
Mod support for UT3 on PS3 is based on the PC toolset. There are no in-game mod tools that run on the PS3. However, this gives an incredible amount of freedom for people to make whatever they want (within reason, after all the PS3 has a limited amount of memory with no Virtual Memory).