Originally Posted by JSanders
Press ALT and ESCAPE. Your running apps will appear.
There are several which you cannot stop: Homescreen, Phone, Address Book, BBMessenger and Browser (just make sure it is not an active browser page loaded), and others according to what 3rd Party apps you have.
You beat me to it! I can only switch between applications here, I don't have the choice to kill them. I have that Outbreak Control game just stuck running and when I go to it all I see is the game's splash screen. No options to end it. Hopefully pulling the battery will kill it.