Here's some of my hopes and dreams for what Joss Whedon will do now.
Faith the Vampire Slayer Miniseries: There's a year of Faith's life between "Chosen" and Buffy Season 8 that could be revealed through a miniseries. It could be used to test the waters on how an actual full blown Buffy spinoff would sit with the Nielsen families. If its a success then it could be turned into a series and we could have a parade and sexy parties to celebrate.
Marvel Comics: Joss will obviously have more time on his hands and writing more stuff for Marvel would be an awesome use of that time. He could work on Runaways again or maybe X-Men... or maybe he could create a new character or group of characters for Marvel.
Dark Horse Comics: Maybe he could create a new comic book series for Dark Horse. Something that isn't connected to anything he's ever worked on before. Or maybe he could write a Sarah Connor Chronicles comic book continuation with Josh Friedman.
Angel Comics: I'd like it if he was a little more involved with the Angel comics.
The Guild: Remember when he guest starred on Veronica Mars? Well I'd like to see him do that on The Guild.