The internet offers so much information for free that this blog is trying to prove that all or most of a college education can be gotten for free online, and on one's own schedule. A couple of months ago, I posted a list of free online learning materials for the GRE subject test in chemistry. There are also a wide variety of materials for biology which are listed below.
Botany Online is an extensive online textbook from the University of Hamburg.
Fundamentals of Microbiology has a good amount of information in it on cell biology.
Ecology from Wikibooks.
Physical anthropology offers a lot of information about evolution.
Molecular Biology Web Book
Molecular Biology-Stanford Encyclopedia of Philosophy