Every year the Environmental Workers Group puts out their list of safe sunscreens. 
When considering your sunscreens remember that last years sunscreen may have expired if you still have some, so go ahead a throw it out and start fresh with a new one this year.

Some important things to consider when looking for sunscreen is making sure you get high enough levels of SPF for your skin type. I know for myself I go from white skin, to red/burnt, and then back to white, so I usually opt for a SPF of 50 or higher. While other skin types don't burn as easily as mine does, so you may be ok with a lower SPF.

Active ingredients that you want to look for are zinc oxide, titanium dioxide, mexaoryl SX or avobenzone (3%) (listed on the EWGs website), while avoiding Vitamin A (retinyl palmitate) and oxybenzone. These last two have been associated with allergic reactions and skin cancer.

Check out EWG's 2012 list before you head out to enjoy the 4th of July!