During the Blender Conference there was a heated discussion on the topic of Blender documentation. Wray Bowling now reports on a new 2.5 feature that was recently added to easily access documentation for any user interface feature.
Look! Right clicking buttons to see documentation got added! For the moment it only links to the python method, which isn't very useful to an artist, but this is a good start. At least it has the potential to be linked to a user's manual of sorts as the 2.5 project moves forward. This is now trunk, so any new build should have it.