You can add a Recent Applications stack to the Dock. To do so, open Terminal and type this command:
After that, type killall Dock to restart the Dock and see your new folder. The only thing is that I haven't found a way to have it show as a fan, it only shows in tile view. But it is already a nice trick.
[robg adds: Once the stack is created, control-click on it to reveal a contextual menu that lets you pick between recent applications, documents, servers, volumes, and items. Note that I've edited this hint to reflect the method shown by mithras in this comment to the Create a System Preferences stack hint.]

