Continuing from the http://www.gamesas.com/topic/1465714-rel-oblivion-script-extender-obse-0021-beta-4/
The Oblivion Script Extender, or OBSE for short, is a modder's resource that expands the scripting capabilities of Oblivion. It doesn't make any modifications to Oblivion.exe, TESConstructionSet.exe, or any other files in your Oblivion install, so don't worry about permanent side effects. As of v0017, OBSE requires the 1.2.0.416 version of Oblivion.
https://dl.dropboxusercontent.com/u/2584752/obse_0021.zip - current stable version, recommended for general use
http://obse.silverlock.org/
http://obse.silverlock.org/obse_command_doc.html - newly reformatted documentation
What's new:
Readme (abbreviated):
For mod developers:
http://oblivion.nexusmods.com/mods/36370 - An OBSE plugin that fixes bugs in the CS and adds new features to it