The recently relaunched ESPN3 online portal is coming to Xbox 360 , as just announced during Microsoft's pre-E3 press conference. Trey Wingo and Josh Elliott from SportsCenter are on stage demonstrating with footage from a USC / Ohio State game, and of course it has built in Kinect controller support. 3,500 live sporting events, instant replays, highlights, polls all at your fingertips or by the sound of your voice. The PiP stuff will be familiar to fans who have already indulged online, but with the new control aspects (and of course, HD streaming) it could give a reasonable alternative to the existing channels. The usual requirement of Xbox Live Gold just like Netflix, Facebook, etc. is present, but beyond having a TV provider / ISP that's signed up for the package, there's no additional charge.
Update: Wondering if you'll have access? Check the list of ESPN3 affiliates to see if your ISP is playing ball.