Not a serious one, but since I don't have the build environment set up anywhere at the moment, I'll just write about it here.
= Compose e-mail plugin =
Basically the same as the search engine plugin, add a "Compose email" action, with sub items taken from a sqlite database with two columns: name and email_address. On "Compose email", it opens "mailto:" (which starts the default mail client) while if you select a sub element (by name) it opens "mailto:<address>".