Yes, there's an app for that! I have MyPantry 2 on my Droid (it's a paid app - .99, I think) and I keep my inventory there. I have one upright freezer and a pullout freezer in the fridge. I can keep my inventory by location, e.g., upright freezer, fridge freezer, pantry, can carousel, etc., and by what it is: beef - ground, chicken - boneless breast, and in alphabetical order.
When I shop, I can scan the bar code with this app and it's added to the pantry, plus I can keep a "price book" with the penny pincher feature.
At the end of the day, I go through and delete whatever I used, and add to my grocery list.
I tried spreadsheets and a white board on the freezer, but I'm just too lazy