Blackdog Media
Classic Reader: Authors: Charles Darwin
This site features the author Charles Darwin including the full text of the nonfiction book Origin of Species.
Other
Evolution: The Theory of Natural Selection (Part 1)
These pages are part of a site called Evolution that accompany a textbook by the same name. Mark Ridley is the author. This section has an advanced discussion of determining allele and genotype frequencies using the Hardy-Weinberg ratio.
Bryn Mawr College
Bryn Mawr College: Evolution by Natural Selection
Students develop their understanding of natural selection by analyzing specific examples and carrying out a simulation.