So right now I am studying to take the CLEP biology test towards becoming a Lactation Consultant. Here is my list of links:
Speedy Prep-this site does cost some to set up an account but it is definitely worth it. I have not been on the new site. The old one just has 400-600 questions per subject. You answer the question and then it tells you the answer right away with an explanation. It will save the questions you missed so you can go back and try again.
Free University Project-this site has a list of links that cover all the areas that the CLEP test does. Some of them are online biology books, some are study guides, etc.
howjsay-this is a talking dictionary that has hundreds of words, even the strange science ones. It's good to hear how to say a word. I can remember it better.
http://www.johnkyrk.com/DNAanatomy.html -this site has 3d animations of several different things, not as many as I would like but the ones it has are helpful
The way I've been doing it is first I read through the Free University part corresponding to the first speedy prep part. I look up anything strange in howjsay, Wikipedia, YouTube, or the 3d animations. Then I answer the questions on speedy prep. I keep going this way till I have done the first hundred questions. Then I go back and retry the ones I missed.
This is the best way I have found.