Good question. There aren't many. Most of the ones I can think of (Kickstarter, Github, Heroku) launched years ago and have since built on their success without really innovating much beyond the initial idea.

The YC portfolio has a lot of interesting, innovative startups. No products that I use myself at this point, though.

Right now, personally, the new idea I find the most exciting is crowd-funding computer games. Last year I spent a ton of money on Kickstarter to fund small indie developers such as Double Fine.

Why? Double Fine isn't innovating. You've played Maniac Mansion, right? Everything else is just incremental variations.

The innovation is the crowd-funding model used to seed non-mainstream (in the sense that these games are all fairly "nerdy" compared to the average Facebook user) stuff with real budgets.