Hype since I first heard about it several months ago. I finally bought it and started figuring out how to use it. As usual, my ideas outreach my time, but I see a lot of potential in using these sorts of simple, interactive, web-based animation tools in so many ways.
I haven't had much time to play with it, but I finally ditched my grander schemes of developing an entire teacher site with it, and chose instead to try developing single, simple applications one at a time. Hype can publish directly to your Dropbox and provide you with a link, so you don't even have to deal with ftp's and domains.
So check out what I did, and test your computer literacy while you're at it: Computer Literacy Quiz.