I am looking to see if there is a way to turn off unnecessary apps on my Motorola Droid.

I use Advanced Task Killer. And every once in a while I'll open the app to check to see what apps are running in the background hogging up my memory and there are about 12 to 15 apps, like alarm clock, and other apps that I haven't used running there. As soon as I kill the apps I get back about 20 to 30 mbs. And about 1/2 hour later they are all up and running again! Has anyone figured out a way to kill all these apps and only have them run when you choose so?