How to quit an app from running in background (ie IM, Skype, etc)

[QQP]

I sometimes use IM / GTalk / Skype / etc, is there a way to Quit the app without trying to Sign Off (and having to Login later)? Or make apps not run in background?

I would rather have the app Quit than run in the background and still remember my credentials.

 

[chikibabe]

Advanced Task Killer??

 

[Grifter]

Advanced Task Killer??

That's what I use and it works like a charm. Saves a lot of your battery as well. You can also choose which apps to ignore (email, Market, etc.). Music and Amazon MP3 are a couple of my biggest culprits that always seem to be getting turned on and runnin all the time before I installed this application.