Last summer I decided to use some birthday money from my parents to pre-order an ESV Study Bible from Crossway. I'd seen enough online to know that it would be a great resource and I was not disappointed when I got it in the fall.
If you haven't already bought a copy of it for yourself, you may be fortunate enough to win one by entering a contest at A Boomer in the Pew. But if you don't win it, you can buy one.
The Study Bible is a great resource--like a concise commentary built into the Bible. I have found it very helpful for leading my Bible Study, as well as my own personal study. There are many good essays in it and the maps and illustrations are phenomenal.
Go to Amazon and look at all the information about the Study Bible there, and I think you'll be impressed. And enter the contest to win a copy for yourself.
03/01/09 UPDATE: Crossway is granting free online access to the ESV Study Bible through the end of March. Go to this link and check out all the content in the published Bible, online.