I don't play often, but when I do, I prefer the Jo1t vCTF server from MTV.
Here is a list with the most active UT3 servers:
http://www.gametracker.com/search/ut3/?searchipp=50
Here is a list with the most active UT3 servers:
http://www.gametracker.com/search/ut3/?searchipp=50
Thanks! That looks like a good resource.