Well, you could use http://www.myp2p.eu/competition.php?competitionid=&part=sports&discipline=baseball. However, most of the links require a small program called TVAnts (download and instructions etc on the site as well) and maybe it's just me, but the streams are occasionally laggy soooo... I personally use it as a kind of last-resort, but for that purpose it generally works fine.
But yes, if I can get my hands on a justin.tv or similar streams I'd pick those any day (seems hard for baseball though)