We just got Costume Quest last month, an announcement for an expansion soon and now word on their new game, Stacking! IGN has a trailer:
Looks like a puzzle game based around matryoshkas - Russian stacking dolls. Smaller matryoshkas can hop inside larger ones to assume their personalities and use their abilities. Seems like it could make for some pretty clever puzzles with you stacking up several dolls to chain their abilities together.
Really love the graphics in the trailer, it looks like stop-motion animation which is fantastic.
I think this new focus for Double Fine is going to work out really well! Smaller, more focused games centered around really simple gameplay mechanics should hopefully let them focus more on the creative and fun aspects.