Macs go to sleep when you close the lid but still take battery power. This DeepSleep widget puts your computer into hibernation, where all the RAM is copied to disk and no power is required. It's great for resuming where you left off if it's going to be a while.
Open System Preferences and select Accounts. Select your user account and the Login Items tab. Scroll down the list until you find the program you want to stop auto loading, highlight it and click on the 'minus' symbol beneath the list.