I use ATK by ReChild. I go to the Settings and and select the "low" security level. Then I go back and uncheck anything that normally syncs stuff so I still get those, like GMail, Email, weather, etc. The rest can be killed and if they are needed, they'll be brought back up.
I usually just save ATK for when I've opened a ton of programs and in case one of the programs continues to run in the background when I'm done.
I still don't know what the program was the other day, but I had set my Droid down with about 40% charge and started working on something with it nearby. Never touched it once I set it down. About thirty minutes later, I get the battery low beep and I was at 15%. So I reach over for the phone to see wtf did it, and my phone was pretty warm from just having been sitting there for thirty minutes.
I am OCd and thought maybe something was screwy with SetCPU, but turns out I had actually decided to be conservative that day and had been running on a 700/550 max/min. So I tapped the ATK widget and killed a good bit of the tasks and then set my phone down. It began to cool off soon after.
So it isn't something I do often, but I'll hit the widget once or twice a day just to clear out any crap that may still be open. If there's ever a debate on TK or not, most people do not do what I do and use it to simply free up memory every 15 minutes. Free memory is kinda pointless since it's there for the programs to use it. The problem, for me, comes in when the app is no longer in use and doesn't idle because the dev wrote the program so shittily. Then I use it.
Did someone suggest to turn window animations off? I hate those.