I checked the EPL, the UEFA Champions League, and of course, Ticky Box, which is my #1 choice.
I used to watch Man U whenever I could be arsed to get up for their games (some have like 8 AM kickoff times and lol fuck that) but that was at school, where I got Fox Soccer Channel. I don't know if I'll be able to watch them at home. If ESPN3 shows games then I'll definitely be doing that. Also interested in the Champions League (though really only the later stages).
I may try and catch Philly Union matches if I can, but the quality of MLS play is pretty poor compared to European leagues, and since Union is an expansion team their player selection is particularly bad (though Sebastien Le Toux is one of the highest scores in the league ATM).
I'm also vaguely interested in the Bundesliga (primarily Bayern München) and various other top European clubs (Real Madrid, Barca, Inter Milan, A.C. Milan, Roma) but I didn't check those because again, I don't know if I'd be able to watch them and I probably wouldn't be interested in watching them on a consistent basis anyway (except maybe Bayern).
All that said, if anyone is looking for a soccer-watching buddy and I'm around, hit me up and I'll probably flip it on and watch, if I have access to it and I'm not busy.