Due to the new agreement (actually, it's not that new) with Major League Baseball and Real Networks, all baseball broadcasts over the internet will now cost $9.95 a year. I know it's not much, but free radio used to be cool.
However, sometimes you can get lucky and go to the local radio station of the team you're looking for and if you click the listen live link you sometimes fluke out.
I've been able to listen to Orioles games here sometimes:
[url="http://www.wbal.com/sports/orioles/"]http://www.wbal.com/sports/orioles/[/url]