Via @lesterbanks on the Vimeo beat is a new After Effects tutorial video from Digieffects, Depth+Camera Mapper Tutorial (below).
There's more info on Depth (a newish filter) and CamerMapper on the Digieffects website, including projects and tutorials. Similar work and tools (Vanishing Point, scripts for AE 3D, etc.) are mentioned in posts tagged multiplane animation, camera mapping, and the AE camera.
Update: Mathew Fuller covers something similar, with techniques for extracting depth from 2D still images in his video tutorial Advanced 2.5D Animation in AE.