I'm a fan of Lore in a Minute!, a site that breaks down a game's lore and story in easily digestible, humorous movies. It's great for if you want to hop into a series midway through without going back and slogging through long, older games.
I headed over there to check out their fun new BioShock Lore in a Minute! video, and wound up going through a few old ones that I'd never seen.
I've wanted to get into the Kingdom Hearts games for a long time. Given the fact that it sounds like we're finally getting another HD version on consoles, it would probably be a good time to bone up on the story I'd missed.