Advanced Task Killer 1.7.6
the author of this app says:
Advanced Task Killer Android App allows you to stop running background processes or apps in memory. The Android operating system can run multiple apps in memory concurrently which currently is its own Gift and Curse. Cursed as some processes and apps can bring an Android phone performance to a crawl. By default, you cant easily close open applications or running background processes unless you go to: Settings -> Applications -> Manage applications -> (wait for list to load) -> (select app) ->Force Stop ;-( Not exactly convenient then The alternative is to download Advanced Task Killer from the market and use that instead. The name says Advanced task killer but it does everything TasKiller does; stops background processes and apps, specify an Ignore List, or kill all apps running with one button (at a higher cost without a home screen widget).
Must be downloaded with your Android mobile phone via Wi-Fi or your wireless data plan from your mobile phone provider. Pro version available @ $2.99.