I was experiencing big battery drainage even using Juice Defender. So, every morning when I booted the phone, I began looking at what services were running. You can do that by going to Menu > Settings > Applications > Running services. I began noticing several apps were on, e.g., Vonage, weather apps, Facebook, etc. Since I don't care about those apps running all day, I killed all those processes. If I want to get the weather I could always click on a weather app and see the current settings. The same goes for Facebook and the others. After a couple of days, I noticed which apps were likely responsible for high battery usage. In my case I think Vonage was the culprit. I ended up deleting it. All others now stay running (FB, weather apps, etc.) without eating up my battery power. I end up the day with an average of 75% power.
My advice: check what's running and especially check any new apps you recently installed.