Via Pharyngula, this old, brief interview with Marti Noxon about negotiations for a direct to DVD movie featuring characters from Buffy. Noxon says up front that they won't be able to get Sarah Michelle Gellar, and they may not even be able to get Alyson Hannigan, but they still might try.
Personally, I'd watch a spin off that featured only Andrew and the cheese guy from the dream episode at the end of Season Four, if the writing was good. Also, and I know this is heretical, I would be willing to see major roles in Buffy played by totally different actors. If many many actors can play James Bond and Clarise Starling, why not Buffy Summers?
Update: While adding the Fray graphic novel to my Amazon wish list I encountered this rather complete list of the major Buffy products available.