Turn off 3G if you don't need it and use GSM mode. Turn your screen brightness down to 3.
Don't use the facebook widget, it's a real battery hog.

Doing this meant I could go from around 12 hours to 24 hours of use.

Over the weekend I turned off the "auto connect to WiFi" option, and yesterday had 49% battery left after 24 hours of use. That included calls, SMS, at least 2 hours on a bluetooth headset and a 2-3 hours using WiFi to check for updates, surf the web etc. (only switching on WiFi when needed).