3D Angel wings with Trapcode 3D Stroke by Chris Lorance

This video covers a slightly less conventional use of the Trapcode 3D Stroke plugin. The 20-minute tutorial explains the creation of the wing strokes, rigging to null objects, and animation and compositing tricks.

Advanced 3D Wings in After Effects from Iaenic on Vimeo.

ADDENDUM
There is a really cool rework and extension of this here: http://vimeo.com/29663169

Dynamic Shadows with Trapcode Particular by Andrew Kramer

Andrew Kramer has a technique for generating shadows for Trapcode Particular.

Watch his awesome tutorial here.

Tutorial: Accurate Reflections in AE by Quba

Quba has made this tutorial on how to create accurate reflections in AE. It is surprisingly simple! And it works for the camera-aware Trapcode plugs such as Particular, Lux and 3D Stroke. Check it out here:
http://qubahq.com/2010/06/tutorial-100-accurate-reflections/