Feel free to post anything I've missed.
There will be 200 computers with SC2 on them. Blizzard employees are attending for interviews and the like. Some of it will likely be streamed. You can watch MLG here: http://www.majorleaguegaming.com/live#sc2
Latest Info: Dustin Browder Interview http://gosugamers.net/starcraft2/features/2934
Abduct (Pulls a unit in)
Blinding Cloud (Reduces units attack range to 1 in an AoE)
Consume (Damages an ally building to gain energy)
Swarm Host: Locusts can attack air and ground
Ultralisk: Has burrow charge, is no longer frenzied. (Now vulnerable to stunning and slowing effects)
Hydralisks: Has speed upgrade.
Banelings: Can NOT move while burrowed.
Overseer: Back in. Can shoot changelings as far as a tank can shoot.
Mothership Core: Doesn't require any tech. Can morph into Mothership. (Requires Feet Beacon)
Energize: Restores a units energy to full.
Teleport: Teleports to another nexus.
Purify: Temporarily grants the Mothership Core a long ranged attack.
Mass Recall: Works the same as usual. Costs 150 energy, I think
Mothership: Cloaking field removed. Vortex only targets ground - Stasis, a new ability that puts the mothership and all air units around it into stasis for about 20 seconds.
Oracle: Built from stargate.
Entomb: Blocks mineral fields from being harvested. You can attack the shield around mineral fields to destroy them, but they also wear off.
Preordain: Grants vision and detection to an allied or enemy structure.
Cloak Field: When casted (costs energy and wears out) cloaks units in an area around it.
Tempest: Requires feet beacon. The tempest is a new capital ship that can fire at both ground and air targets from long range, doing additional damage to massive units. A further range upgrade can be researched to give the Tempest the ability to fire from incredible distances. (Note: Starts at range 10, increases to 22 range with upgrade (compared to 13 for siege tanks). Said to have relatively low DPS to balance it out.)
Widow Mine: Description: The Widow Mine is a new suicide unit built from the Factory that allows the terran player to control areas of the battlefield. The Widow Mine moves into position and sets to stationary mode, which burrows and activates it. When an enemy air or ground unit moves into range, the Widow Mine briefly flashes before moving and attaching itself to that unit. After several seconds, the mine detonates, dealing 200 damage to the unit and a smaller amount of damage to units in the surrounding area.
Note: Dustin Browder expects that with practice, pro-level players will almost always be able to remove the mined units away from the rest of their unit cluster.
Warhound: The Warhound is a walking ground mech that is specialized as an anti-mechanical weapon. Smaller and more nimble than a Thor, the Warhound has a standard weapon to hit ground. Its true strength is an additional ability that fires powerful missiles at ground-based mechanical units, making it particularly well suited to taking out enemy siege lines and many protoss ground units. Note: anti-mech missiles auto-launch at mechanical units independent of the warhound's normal attack.
Thor: Back to WoL-style.
Battle Hellion: Same as before.
Battle Cruiser: Has a speed boost ability called Redline Reactor.
Reaper: Regen, no building attack.