I've finally managed to upload a version of my PowerPoint LaTeX add-in for PowerPoint 2007.
I'm just going to post a short Vimeo video here that shows how inline formulas work (the main feature):
I've tried to work on the add-in during my spring vacation but somehow I have instead spent all my time watching four seasons of House M.D. (which was totally worth it though 
).
There are still some features like support for MikeTeX, code clean-ups, small bugfixes and a preference window that I should work on, but I don't plan on selling it, so I don't really care if it's still somewhat work in progress.
I'm going to continue working on it when I have to use PowerPoint again.
You can check it out (and another add-in dubbed Language Painter that I wrote to fix some annoyances when writing presentations in languages different from your keyboard layout) at http://code.google.com/p/powerpointtools/.