External Vote Buttons (EVB) are included in the Beta 6 release, but I haven't released any documentation for them yet. Expect a tutorial for that in the near future when I get around to making some new Pligg tutorials next week. As a quick hint, check the /api directory (
http://demo.pligg.com/api/) of your install. You will have to manually edit the files right now to make them work with your own domain rather than the demo.pligg.com domain.