The Red Giant sale is over but Digieffects' 30% off holiday sale on their Megasuite is good through Friday. The Megasuite is Damage v2 (7 filters), Delirium v2 (45 filters), and Buena Depth Cue v2 (6 filters extending 3D functions of After Effects). On Monday, some individual Digieffects filters will start to become available ala carte.
Note: Toolfarm is also having sales this month, for example Video Copilot stuff is 25% off through Friday!
Here's an example tutorial for Falloff Lighting, part of the Depth Cue package: