another vote for Neutrogena dry touch sunblock. It says it's for face, spf 60 but I use it all over the arms and legs too.

Either way, the best way is to reapply sunscreen often. I usually go to the cosmetic counter and try and get free samples so I can tug them in the seat pouch. I've used some over the counter brands sunblocks too but I find them expensive and since Neutrogena works well and doesn't cost an arm and a leg, I'll just stay with that one.