Good thoughts. I do have a retail disc of iLife 06, so I can give it a shot. You would install the program on your Mini the same way you did the OS. Use the disk utility on a Mac and 'restore' the installation disc to a USB drive. When you plug the USB into your Mini, it will look like the installation screen you see when you insert the disc into a DVD drive.
By way of update, both Skype and Quicktime recognize the onboard webcam, but iMovie 09 does not. As long as I have a means of inputing video, I am happy, so Quicktime is a good fix. Anyone who would prefer iMovie, you might also try Kenchen's solution (iMovie 06 was a thing of beauty anyway).