Glow-in-the-dark filament is brilliant. I got mine from reprapworld.com. Getting the extrusion temperature right so that the filament didn't ooze out of the nozzle all over the place took a little time but it is ideal filament for printing Halloween goodies.
I started with some simple objects from thingiverse. First I printed a couple of glow-in-the-dark spider webs:
Then a brilliant glow-in-the-dark vampire skull:
Then I decided to make a 3d print version of a card that Reuben made at school using a hand print:
I took photographs of their hands with a dark background, traced them in inkscape, scaled them to actual size, converted them to dxf files (using this process) and used openscad to extrude them. They came out quite well and are now hanging under their beds.