I'm curious, because we all know about a lot of them. I, for one, watch sine of the other shows our beloved actors have gone on to do (like HIMYM), as well as a few of their movies (I just rented Repo! the Genetic Opera and look forward to it). But I don't watch all of them (I haven't seen Gossip Girl, for example).
So here's my list of other things I watch and love that has a connection to Buffy.
The Whedon Shows (all of them)
How I Met Your Mother (Alysson Hannigan, Alexis Denisof, Amy Acker)
Bones (David Boranaz)
Torchwood (James Marsters)
Dexter (Julie Benz)
Desperate Housewives (Nathan Fillion, Julie Benz)
Castle (Nathan Fillion)
Veronica Mars (Charisma Carpenter, Joss Whedon [Cameo])
As for movies, I've seen Scooby Doo and the Grudge, but wasn't partial to either. I have never seen Cruel Intentions, but I want to. I also saw I Know What You Did Last Summer, but I preferred the book.
I'm looking forward to Repo! The Genetic Opera, though. As an avid Rocky Horror fan, I am super stoked to see it. Especially because Anthony played Frank in a Rocky Horror Revival, so I'll bet he's suited to this role.
What shows do you guys watch?