The science of human evolution is called physical anthropology or paleoanthropology. These scientists study ancient fossils in their search for what makes us human. The first discovery of modern paleoanthroplogy was the skull of a Neanderthal man in 1856 in a valley east of Dusseldorf, Germany.
"Just over three million years ago, an ape in Africa began to walk on two legs and took the first step on the long road to civilization. Along the way, we discovered flint tools, fire and farming. But what is it that makes us truly human?" BBC has a great collection of articles (just click your way through the section headings to find them) as well as games and quizzes (look in the left-hand column under Prehistoric Life and in the right-hand column under Related Links.)
The Institute of Human Origins is a research and education institute now associated with Arizona State University. Start with the Interactive Timeline feature, that takes you back seven million years to explore evidence found by paleontologists all around the world. The oldest discovery on the time is the skull nicknamed Toumai, and found in 2002 by Michel Brunet and his team in Chad. For printable classroom handouts and online games, visit the Learning Center.
Built as a companion to the seven episode 2001 PBS television series, this site still has lots of valuable content. Whether you explore via the "For Students" link or jump into any of the episodes from the front page, you'll reach the same videos and related web activities. For a newer version of the website (which includes full video from more recent shows), click on the "Visit NOVA's new evolution site" banner. Be sure to watch Early Humans in Pop Culture. "For 150 years, pop culture has offered distorted images of our ancestors."
"Human evolution is the lengthy process of change by which people originated from apelike ancestors." From the National Museum of Natural History, this mega site is chock-full of goodies for both students and teachers. This page is a short introduction to human evolution and paleoanthropology. Other great clicks are the Mystery Skull Interactive, Fun Facts ("While other primates are furry, human skin is exposed to the elements.") and a clickable human evolution glossary.
"The central idea of biological evolution is that all life on Earth shares a common ancestor, just as you and your cousins share a common grandmother." Understanding Evolution is a collaboration between the University of California Museum of Paleontology and the National Center for Science Education. It includes an online course (Evolution 101), a searchable archive of articles and tutorials, and teaching materials for grades K-12 and college undergraduates.