Epic has been saying all along that Sony's "embracing" of user-created content is one of the big reasons Unreal Tournament 3 debuted on the PlayStation 3. Also, existing mods are always fun to toy around with, and if you want to nab 'em, a very helpful tutorial has surfaced in the official PlayStation forums.
As you can see at the link provided below, a member has supplied a step-by-step set of instructions for downloading UT3 mods directly to your PS3. It's not an over-complicated process, but for the uninitiated, it could be immensely annoying without some help. You even get the benefit of visual aids here, so make sure you give it a look-see if you plan to use mods. One of the best shooters of the year doesn't necessarily need any modifications, but there's no fun in playing the exact same level over and over, is there? And besides, that tutorial also works for Map Packs, and all you need (outside of the PS3, internet access, and a copy of the game) is either a USB flash drive or memory card. You gotta transport the data somehow, after all.
If you're interested, visit the tutorial in this thread at the PlayStation forums. Be nice and say thank you, then move on to downloading any mod or map pack you desire.
Related Game(s): Unreal Tournament 3