I'm looking for a way to produce a not-to-nasty-looking (fake!) burn on an actor's forehead. Any suggestions?

You could try this-theatrical makeup. Look for the coagulated version of the blood. If you need a shinier, burned/blistered look, you'll need to add a shiny base, see the Effects Gel Wound Kit or mix with Karo/corn syrup, maybe apply over white carpenter glue, Elmo's or similar base pad.

http://stageandtheatermakeup.com/mhblood.htm

Check out the rest of the product lines-Mehron and Ben Nye

Good luck

iPaul

Good link, thanks.

Does anyone know if make-up artists have a web-community I could crash?