Telltale's Back to the Future series of adventure games is a favorite of mine. They're packed with classic BttF stuff and the voice work is outta this world. But if you've been on the fence about them, now's the time to get on (hover)board. The game's are available on PC, Mac, PS3, and iDevice- but from now till September 30th, the iPad versions are on sale for $2.99 each.
I can't recommend these games enough if you're a BttF fan, or even if you just like adventure titles. You can get 'em (starting with episode 1) right here.