It seems like I've been going to the grocery store every day this week because I keep forgetting things when I'm there.  So when I saw this "All Out Of" notepad sticks to your fridge, I thought it would be really useful.  You can get them at Franklin Covey, Stacks & Stacks and many other places for about $7 per pad.

Or you could find a free grocery checklist on the web like this one at printablechecklists.com, or make your own!