Yeah, it's available again for free play; though you do have to create a Steam account and download the free client. Well worth it in my opinion as UT3 is a brilliant game. IF you've got the time to play it all weekend I'd recommennd downloading some of the better mods from fileplnet or filefront. You can usually find a list of the more popular mods at both these sites.
For example The Titan Pack Expansion , Angels Fall First: Planetstorm, and the haunted Mod. I'd recommend fileplanet, but it's easier to download from filefront unless you have a subscription at fileplanet (it's not needed, but you usually have to wait in line sometimes for up to 20 or more minutes during peak times, and then you can only download one file at a time and at the slowest speed. I download masses from fileplanet, so get a years or two years sunscription usually, which enables me to download up to 10 files at a time using the fastest servers, plus I can que more if I wish. I've used that facility often when I'm downloading mods and maps for a newly bought game.
Check out UT3 mods and maps from Filefront HERE
Check out UT3 mods and maps from Fileplanet HERE
regards
Stephen