many apps running at once

[boneskid1]

hello all im new and never really posted just did some lurking then i put android 2.2 on my tp2 but i am having some troubles more recently most of my apps will open and continually run slowing down the speed of everything making it a horrible device to even work with. so i founda few threads that explained that they are just ready to be opened but if that were true it would not be hogging the processing speed. so i guess what im asking is, is there anyway to get the apps to stop running, and if i have to install a app killer what is the most trusted one to use?
Thanks,
Boneskid1