I'm not so sure there are any truly credible resources out there. Most are based largely on anecdotal evidence and don't come anywhere close to the rigorous testing required by scientific standards. PubMed is a good place to look for peer-reviewed articles, but there probably aren't that many on subjects you're interested in. Also, the articles are quite dense and you will probably need to take a trip to the library to gain access to the articles. Even the Journal of Cosmetic Science looks like it's pretty much all industry-sponsored research so naturally it's going to be biased...
I was skeptical when I first found the curly chemist articles on this website, but I appreciate that no specific products are recommended and that the logic is clearly laid out.