Gridder arranges layers into various grid configurations.
-Rectangle -3D -Circular
Copy the file "Gridder.jsx" into the following folders:
Windows: C:\Program Files\Adobe\Adobe After Effects CS[x]\Support Files\Scripts\ScriptUI Panels
Mac: /Applications/After Effects CS[x]/Scripts/ScriptUI Panels
You should allow scripts to write files Edit->Preferences->General->Allow Scripts to Write Files and Access Network