ESPN, ESPN2, ESPNU, FOX, FS1, FS2, ABC, NBC, CBS, NBC Sports, local sports networks (NESN and whatever channel the Celtics play on is called for Boston area), TNT, NBATV, MLB Network.

The pricetag is high at $50 and I wouldn't be surprised if in a year from now there is another price hike, but the key there is to find a buddy or family member who also wants it and you split it. If you open an account all you have to do is add their email as a family member and they have access to it when they log in with their email (rather than a shared log in a la Netflix). I split it with my Uncle so I pay $25/month.

One of my favorite features on YTTV is you can customize your channel guide so you can reorder channels and put your more watched channels at the top, group by category, and remove unwatched channels (Disney kids, Telemundo, Fox News, etc)