I have found a pretty good website that gives some good information about sunscreens. (I usually take the information I find and double check it on wikipedia & do other research.) It's called Environmental Working Group, or EWG. They are kind of like a Consumer Report, but specialize in personal care products. Their website adddress is: cosmeticsdatabase.com, but it has a category for sunscreens as well.
Here is an excerpt from their site on Sunscreen.
SUNSCREENS: HOW IT WORKS, WHAT IT MEANS
Which sunscreens are best and why?The ideal sunscreen would be highly effective at blocking both UVA and UVB rays, contain active ingredients that do not break down in the sun (so that the product remains effective), and contain active and inactive ingredients that are proven to be safe for both adults and children. Unfortunately, there is no sunscreen that meets all of these criteria, and no simple way for consumers to know how well a given product stacks up on any of these fronts — which is why EWG created this guide to safer and more effective sunscreens. To see how we conducted our analysis and ranked products,read our methodology.
When picking a sunscreen look for zinc oxide or titanium dioxide, avoid oxybenzone and sunscreens with fragrance. Choose a product with an SPF of 30 or higher, avoid sprays and powders and bug repellant.