Thanks to NWA's ignorant post, I felt compelled to find something that NWA could understand regarding speciation. I think this excellent video should do the trick:
For a fuller discussion of macro-evolution, Talk Origins has a series on predictions based on evolutionary theory and the results that confirm the theory.
Note: A theory is not the same as "hypothesis," which is a preliminary guess. A "theory" in science is a concept that explains observed phenomena, and which can be further tested with more observations. So far, observations by trained biologists have confirmed and refined the theory of evolution in many ways. Observations by Christian pseudo-scientists have been debunked by responsible actual scientists. Note: these scientists are not "Darwinists." They are scientists - they trust the scientific method to add to human understanding, and do not revere Darwin at all except in the same way they revere any scientist who has proposed a new theory that has stood the test of time. They are not "Darwinists" any more than they are "Newtonists" or "Einstinists."