"They Might Be Giants" has a knack for making catchy tunes. Their most recent offering, Here Comes Science, is targeted toward school children and is (obviously) very science-centric.
Here's "I Am a Paleontologist", which I now cannot get out of my head:
You should also check out Science is Real because, well, it is.
UPDATE: Boing-Boing's "Meet the Elements" is also damn good sciencey stuff!