Where was this when I needed it in college? I always needed advice on which food expiration dates are strict rules and which are just guidelines, I never knew how to defrost different foods safely and I would have no answer when a dorm mate asked if it was OK to re-freeze thawed meat. Thankfully, we have the internet and there is an easy guide to figuring out how to not kill ourselves with unsafe foods...
StillTasty.com is the ultimate shelf life guide. Tell it what leftovers—ahem, fresh groceries— you're storing and it will tell you how long it's OK to keep it in the refrigerator or the freezer. It'll also give you tips on the best ways to store it.
But my favorite feature of the site is the "Your Questions Answered" section, a suitable replacement for calling mom every night. There you'll find the answers to such perplexing matters as "I Left Pizza Out Overnight—Is It Still Safe to Eat?," "Do You Have to Refrigerate Opened Bottles of Mustard and Ketchup?," and "Is it OK to Put Hot Food in the Refrigerator?"
(For the record, the answers to those three are no, no and yes.)