The 50mm f1.8 Prime is one of the best lenses Canon make - period.
It's an absolute bargain, and is capable of some stunning shots. True, the lens is made of plastic, and the auto-focus is noisy and clunky, but I forgave it all that the first time I checked the kind of images I get from it.
Also, using a prime lens makes you think so much more about composition, rather than just 'zooming' to fit somethiing into frame; often I enjoy just taking the 30D and the 50mm prime out, and never fail to come back with some good images - its low-light performance is cracking, too!