exe: http://dl.dropbox.com/u/12654979/EnableAddons.exe
virus scan: https://www.virustotal.com/file/6ce4...is/1336224936/
source: http://dl.dropbox.com/u/12654979/EnableAddons.cpp
Just run the exe and it will patch any open wow.exe it finds.
Also, note that the addon api is a bit incomplete atm (several functions seem to be either missing or renamed) so don't expect all your addons to run flawlessly.
Updated to a (hopefully) build independent version (thanks to TOM_RUS for the pattern)
Or if You prefer a permanently patched wow.exe look here (MoP beta - Enabling addons) (thanks to Ssateneth)