I linked to the awesome AppleScript efforts of Chris Sauve before. But this time Chris took it out of the field with the recent update to his already impressive OmniFocus Project Template script.
While not really a "plugin" in the strict sense – that would require OmniFocus to have a plugin architecture – Chris' Templates script has reached a maturity which can easily be considered plugin-like.
Next to this useful screencast the script's project page has a very detailed and illustrated description as well. We can consider the 'template problem' solved now.