Here is a really interesting plugin. I don’t know how useful it would be to the masses at large, but for technical people it could be a lifesaver.
The purpose of ubernyms is to allow you configure a set of frequently used abbreviations that will be automatically encoded nicely whenever you use them. The goal is to make them visible in a way that is literate for both humans and computers. In other words: we tag them appropriately for your computer, and expand them as necessary for humans.
Check it out at Huddled Masses.