Three huge events figure to make this weekend one of the biggest ever in competitive video gaming: the EVO World Championships, the GSL Finals and, underway right now, MLG Anaheim. Reminder: MLG Anaheim's championship round is underway now. You may see it here.
StarCraft 2, Halo: Reach and Call of Duty: Black Ops are the events, currently in pool play for the rest of tonight and all of tomorrow during the day. Elimination and consolation rounds will begin at 9 p.m. EDT/6 p.m. PDT tomorrow.
MLG promises two livestreams for StarCraft 2 and one each for Halo: Reach and Black Ops. You can see a full schedule of listings here.
You may watch live, for free (with ads) through MLG's front page. If you want all of the streams, ad-free, MLG is offering league memberships or single-event passes for that.