Yeah and he's going to star in a new TV drama call Drive, it looks interesting!
Actually, you're probably thinking of Nathan Fillion, who played Captain Malcolm Reynolds in Firefly/Serenity. He's the one who's going to star in Drive. (Hey, Fillion also did voice work for the Justice League cartoon. Neat.) Fillion has also appeared on Buffy in 5 episodes in 2003.
Joss Whedon is the writer/producer for Buffy, Angel, Firely and the Firefly movie Serenity. Although he has appeared once in each of his TV series, he's not usually considered an actor. Whedon has also written some comic books: Astonishing X-Men that I mentioned above and also comic adaptations of Buffy, Angel and Firefly/Serenity.
Sources: Wikipedia and IMDb (fact checking my personal knowledge)