Nor is it as realistic as methods taught in fxphd's April term course Nuke 2D to 3D Stereo Conversion. For related developments on the higher end, see fxguidetv: Flame/Smoke 2011 Releases or fxguidetv #079.
Anyway, RealVision.ae has ideas on how CS5’s Rotobrush and Nuke Ocula tools assist in 2D to 3D conversions. And Imagineer Systems profiled the use of mocha as a VFX tool in the "Dimensionalization workflow" of In-Three; see In-Three: 2D-3D workflows. George Lucas called some of their work "shockingly good," so check out In-Three's basic technical docs for ideas, and In-Three on the Workflow Behind 3D Conversions on Studio Daily.
Other discussions of 3D in CS5 and in AE were noted previously in 3D, Cineform, and CS5. And here's some fun via Tim Sassoon from a recent thread on the AE-List on 3D and its hype, 2D Theatre by Hungry Beast -- and something more like the future via the Twittersphere:
Update: Andrew Murchie has launched a four-part series of After Effects tutorials showing how to convert 2D footage to 3D. Each one focuses on a different technique with an increasing level of complexity. 2d to 3d After Effects tutorial, the first tutorial, covers a simple channel offset technique that will get you converting 2d to 3d.
Update 2: fxphd has an April term class, Nuke 2D to 3D Stereo Conversion.