We reviewed FullerScreen prior to the 1.0 release in April. Since then, FullerScreen has added a slideshow mode that lets you use Firefox to show presentations. See this W3C slideshow prepared by FullerScreen developer Daniel Glazman to test the slideshow mode. Hit F11 with FullerScreen and it will ask if you'd like to enter slideshow mode.
To learn how to make your own slideshows, see Glazman's projection test mode document, which works as a slideshow and describes the necessary elements to create a slideshow for Firefox.
If you're already using FullerScreen 1.0, the new release is available now via the Firefox Extensions Manager, or you can download it from the Disruptive Innovations website. You should be able to find it at FireFox Add-ons shortly.
It has been tested on Windows and Linux. View the test case and explanations document.