One thing that Flash is born to do is screen savers. Screen savers and Flash should be a match made in heaven. Problem is that the SCR format is pretty restrictive. It's basically a standalone EXE that gets passed information about how to display itself, show its settings, and respond to Windows messages when it's time to die (i.e. when the user moves the mouse). Flash doesn't handle that.
Fortunately, most Flash EXE-builders can build screensavers that handle all of that stuff for you. I've been using Zinc for EXE-building, but its screensaver support is pretty mediocre. The only real option you have is to add a bitmap that'll display as your screensaver settings. I wanted the ability to change the settings of a screensaver, and it appeared that Zinc just wouldn't do it.
Enter Screenweaver. Screenweaver is a similar Flash EXE-builder. Right now it's very much in a state of flux. After a couple of years without an update, the author decided to open-source the whole thing. It's had a couple of minor updates since then, but most work has been devoted to a version 4 that's on the horizon.
Screenweaver's screensaver support, however, is top-notch. I can set one Flash file for the screensaver and one for the setup screen. I made a tiny little Flash file with buttons and saves settings out to the registry. The screensaver can then read those values and everything's happy.
It's not perfect. For one thing, I have to restart the Screenweaver build environment every time I want to build my SCR, as it gets lost after a couple of builds.
So I'm happy. I'm making a couple of screensavers. If there's any suggestions for a screensaver you'd like to see, lemme know.