Qbeh: a free block-based puzzler inspired by Portal and Minecraft
Developers Liquid Flower Games might play up the Minecraft and Portal similarities on the Qbeh homepage, but I think that's doing their serene puzzle-FPS a disservice. (And besides, if the game resembles anything, it's Toxic Games' Q.U.B.E.) Available now for free on Desura, Qbeh tasks you with traversing a series of short stages, solving problems by planting blocks in the environment. In that sense alone it's a bit like Minecraft, while the perspective and white-washed walls can be traced directly back to Portal.
The video below (taken from an earlier build) suggests the game has an ambient, abstract character all of its own, however, so if you have a slot in your heart for one more cube-based puzzle game, Qbeh just might fit right in.