MLB At-Bat '11 (if you like baseball, you can listen to any game and get other videos, news, etc. - unfortunately, no live video feeds of games like the iPhone version)
ESPN
NFL Mobile
ScoreMobile
There are others for soccer, etc., that others can point you to, if those kind of sports are your thing. Me, I'm a baseball, football, college basketball, college football kind of guy, and those apps suit me just fine.
I use the ESPN app and Score Mobile. I like being able to add scheduled games to my calendar with Score Mobile. I enjoyed that feature when I had it on my BlackBerry as well.
Posted from my CrackBerry at wapforums.crackberry.com