I like to check the Skin Deep Ratings of products before I buy them, but in order to do so I need the list of ingredients. Unfortunately, a lot of companies don't provide the ingredient lists for their products online. Here are a couple of websites that I turn to when that information isn't listed on the company's site:
This website is run by Paula Begoun and gives research-supported reviews of cosmetic products. Paula is big on identifying skin-irritants, which, regretfully, include many natural ingredients. Each review examines the product's claim and gives Paula's professional opinion on whether or not it is warranted.
This is an online community for beauty consumers. Create an account, and you can read consumer reviews posted by other users, post on the message boards, and arrange swaps. The review page of an individual product often contains the product's ingredient list. The ingredients are added by people like you and me, so there are spelling errors sometimes, but I can usually figure out what it's supposed to say.
Once I have the ingredients, I see what Skin Deep has to say. If I want to do a little bit more reading, I'll google the ingredient or search for it on Stephanie's Chemical Database