One good place to start learning about evolution is the PBS Evolution site, with great videos and lots of general information.
The Smithsonian Institution human origins site and the Becoming Human website provide information and resources on the science of human origins from people who actually study it.
Check out the new NSF site "Evolution
of Evolution."
A really great website for learning about how science actually works, especially for teachers and students of science or any other subject.
Probably the best web resource on evolution for teachers, students, and everyone else is the UC Berkeley Understanding Evolution website, "a non-commercial, education website, teaching the science and history of evolutionary biology." It has tutorials, teaching materials, current research information, and a lot more.
A review (with commentary) I wrote for the scientific journal Evolution & Development (written for an audience of other scientists): Postcards_from_The_Wedge.