My battery was dying so fast it was insane. Then I started to do some research. The default refresh time for the built in email app is 5 minutes. I have 4 email accounts setup. I changed the email refresh times to a more conservative 1 hour since most my emails are not time critical. Since then my battery is holding out much much better.
Go into the email app
press the menu button
press on send & receive
press on set download frequency
change this to something more reasonable.
you will need to repeat this step from each of your email accounts
go to the main mail list in each account and follow the steps.
I'm sure there are similar settings for most the widgets/apps that update regularly.