Blizzard has shown four internally-developed mods for StarCraft II at BlizzCon, all of which it will be releasing for free download: Blizzard DOTA, StarJeweled, Left 2 Die and Aiur Chef.
The biggest project of the four, Blizzard DOTA, is "further out" from release according to StarCraft II producer Chris Sigaty. A variation on the ever-popular Defence of the Ancients, which began life as a Warcraft III mod, it's a competitive map for single hero units - in this case, drawn from across Blizzard's franchises ("a bit like Super Smash Bros").
In the BlizzCon demo, Raynor, Kerrigan and Zeratul from StarCraft fight alongside Sylvanas and Muradin from Warcraft and comedy hybrid characters like Grunty (a baby Murloc in a space marine suit) and Level 80 Elite Tauren Chieftan, the mascot of Blizzard's house band.
StarJeweled blends a riff on PopCap's puzzle classic Bejeweled (Blizzard's friends at PopCap preferred the title BeZerged, apparently) with a tower defence (or rather, tower attack) game. Completing rows of gems on the right of the screen sends out units on the left to attack an enemy base, also building energy to spend on additional summons.
Aiur Chef is a game of exploration, collection and cooking. Your Protoss chef, brandishing a cleaver and wearing a pot on his head, explores a map collecting ingredients to use in set recipes (themed around a certain ingredient, as in the Iron Chef TV show). The more you can complete before a time limit expires, the higher you score.
Left 2 Die tips its hat to Valve's Left 4 Dead in its spin on the StarCraft II: Wings of Liberty campaign mission The Outbreak. It's a co-op map for two players in which you need to defend against waves of undead at night while burning their nests by day, with special undead units inspired by Valve's infected.
The latter three mods will be available "within the next few months", Sigaty said.