What kind of plugin documentation would you consider actually useful?
At the very least a list of the plugins with their features would be nice. Also, some descriptions of what the inputs in the config do, like the openvpn config, I wasn't aware of the openvpn management interface so that ui left me a little confused as to what I needed to do, a tooltip or something about that would be nice. Just things similar to that would help out the user experience a lot.
Ajenti is on GitHub, feel free to fork it and start creating Wiki articles.  Being as though he is the only developer working on this and it's being given out for free, documentation is normally on the back burner as there are bugs, and features that would be considered higher priority.

:) I'm just sayin...