Adobe is shipping CS 5.5 and has made it available for download. The list of resources for this upgrade so far is short but deep:

After Effects CS5.5: What’s new and changed and more recent articles by Todd Kopriva.

After Effects CS5.5 New Creative Techniques by Chris Meyer, on PVC and AdobeTV.

After Effects CS5.5 New Features by Mark Christiansen is new. It covers the relevant new features of After Effects CS5.5, including the new Warp Stabilizer, 3D Stereoscopic workflow, Lens Effects tools, light falloff, and workflow improvements. Exercise files are included with the course at Lynda.com, which has various free trials offers.