Protector
Currently only in planning stages.
Pretty much, the enemy creates custom units to send against 5 players who each build barricades with custom units and towers behind them. The enemy's units try and destroy a building on the bottom of the map.
See forum thread for more details: http://forums.sc2mapster.com/development/project-brainstorming/366-sc2-map-idea-currently-unnamed/
I have very little map-making experience but learn fast and would be a capable terrain editor. I would also like to help with beta testing. I don't expect anything but a good experience and a name in the credits. I think you have a great concept and would love to see it come to fruition.