We're using ccnet at work, which is fine for most of our needs (we have about 50 automated builds), but it needs one person for full time tweaking and fixing.
If you're starting from scratch, please take a look at Bamboo. We have looked into it and it looks really promising, but it doesn't completely match our needs and we have invested way too much time in ccnet to switch to Bamboo now.
Regards,
Sebastiaan