No, it’s not from Gridiron, and it doesn’t do any of the cool preview rendering, but BG Renderer, from the AE Enhancers forum, does do background rendering, for free!

Using the power of After Effects scripting, it opens a terminal or command line window to background render any queued items.

It also had the added advanced feature to launch more than 1 instance at a time. If you have a multi-processor machine, you can launch as many instances as you have cpu’s. In my testing, this cut render times in half on a Quad G5 using 4 intances. (having at least 1 GB of ram per instance launched is recommended).

There’s lots of error checking behind the scenes so I did some beta testing to make sure it doesn’t have any bugs, but as always please share anything (good or bad) that you encounter.