Are human beings the descendants of chimpanzee/pig hybrids? This radical theory might seem easy to disprove, but "decent arguments against the hybrid origins theory are surprisingly hard to find."
Becoming Human is a site by the ASU Institute for Human Origins, and its focus is human evolution and the hominid fossil record. Equally notable is the Smithsonian's Human Origins Program. Perhaps the most in-depth site I've found, however, is Modern Human Origins. It's incredibly detailed (down to diagnostic characteristics of individual fossils), and accurate as far as I can tell. Just don't forget about Sahelanthropus Tchadensis, the most recent and oldest (6-7 million years) find in our possible family tree. Good stuff for Science Saturday.