I have to edit some code for a wiki. For Latex, Vim-Latex is a great help writing the stuff in my favourite editor, Vim. But it do not fits all my needs for editing Wikis, of course. That is why I have written a short snippet for the snipMate plugin: Wikipedia.snippets. You have to add this i.e. to your local vimrc directory: ~/.vim/snippets/ . The shortcuts are similar to the ones used in Vim-Latex. Please note: I add a snippet when I need it. So the file is really not complete or even finished!
On Wikipedia you can find a help page with basic instructions using Vim for editing Wiki text.