A few of my favorite links:
- Business Week slideshow on Shelf Life
- Real Simple's A Guide to Food Expiration Terms: Decode the sell-by and use-by dates
- WebMD's Do Food Expiration Dates Really Matter? Excellent section on page 2 for basic rules for how long food is safe to eat, and how to stretch the shelf life through proper storage.
- Real Simple's How Long Can You Refrigerate or Freeze Food?
Edited to add: Home Food Safety (thanks, danae!) There's two great printouts at the top right hand side to hang on your fridge or freezer.
And don't forget cosmetics! I generally try to sort through my makeup 3-4 times a year. Ideally, I should be doing it once a season. Creamy or liquid products have a shorter shelf life than powders once they are opened.
For lotions and such, I prefer pump dispensers or squeeze containers than dipping my fingers into a jar. Not only does it reduce the bacteria introduced to the remaining lotion, but it cuts down on the oxygen exposure.