This is a seriously useful site for figuring out which sunscreen is likely to protect you and which might actually cause you harm. The Environmental Working Group is a non-profit, non-partisan research organization that performs studies on products to see how they affect consumers and the environment. According to their Cosmetic Database Sunscreen Report, “An investigation of nearly 1,000 brand-name sunscreen products finds that 4 out of 5 contain chemicals that may pose health hazards or don't adequately protect skin from the sun's damaging rays. Some of the worst offenders are leading brands like Coppertone, Banana Boat, and Neutrogena.” The top brand, deemed to pose no risk to the user and which worked best, was Soléo Organics All Natural Sunscreen. Congratulations to them. I'll be putting in my order right away.
Check out the EWG study and see if your sunscreen is safe: http://www.cosmeticdatabase.com/special/sunscreens2008/findyoursunscreen.php