You are probably looking at something like ROM Manager and/or Titanium Backup. Both of which will require you to root your phone to run, and I am having a minor issue with Titanium Backup, but I have not tried to work through it yet.
ROM manager can take a snapshot of your phone for easy recovery, and Titanium Backup can backup all your apps for easy restoration.
If you are running stock, you may want to instead look into the "hokey pokey" you have to go through in order to have your apps reinstall from the Market if you have to reset your phone ever. It sounded like something you have to get right the first time, or buy your apps again... but no rooting of your phone required.