Our intrepid blog scout Rox of Spaz-House is on the case again, reminding me of something I actually listened to earlier in the week, so I can vouch for it: The Bride of Monster Mash-up, an entire album of Halloween-themed remix gold. Apparently there's a bonus disc as well, which I didn't catch before. She found that over at Boing Boing. Update: The main site is down and I can't find a download link anywhere. It does appear that it's available if you search for torrents, though. Good luck.
Also, Senses Working Overtime is providing 31 days of Halloween goodness, with a stunning array of treats: classic radio shows, comic books, and e-books of horror goodness. Very impressive. The roundup of their first week is here.