Pit of Infestation by Slarti
Pit of Infestation is a coop-ARPG map for up to 4 players. Every player chooses a hero with specialized abilities in order to stop the Zerg from infesting the planet. It's currently scheduled to be released before patch 1.5 goes live. You can check out the project thread here.
Also, for those who are interested, blizzard posted a Terran Vs Zerg HotS Battle Report a few days ago. You can see the video if you haven't seen it yet.
About the TvZ Battle Report: Reapers lost their D8-Charge weapon, their Gauss Pistol weapon range was increased to 7. Their life was increases to 60. Train time reduced to 40. New upgrade at the Tech Lab, Combat Drugs, that allows Reapers to regenerate life when not in combat. Speed upgrade removed.
Widow Mine: New Factory unit to replace the Shredder. It burrows and when a unit moves near it (air or ground) it attaches itself to that unit and detonates 10sec after dealing 200 AoE damage.