If you mosey on over to the software section, you can grab version 1.2 of the Slide Toggler script. It has a very minor addition which was requested, and that is an auto-reset timer: in addition to clicking slides to toggle them between foreground and background, it lets you optionally also specify a time after which foreground slides will automatically revert to the background. This is probably more useful for public displays, where other users can toggle the slides, than for presentations... but feel free to use it however you like! Open source, as always. :-)