I was lucky enough to receive a Google Wave invite and am using it to collaborate the meal planning with the husband, the mother and the mother-in-law. We can all make edits to the original list as we change our minds or buy the necessary ingredients! So far, this is the most well-planned Thanksgiving we have ever had.
From: Some subset of the Parenthacker crowd:
WHAT'S GOOGLE WAVE?
Google Wave is a nifty new collaboration tool that blurs the line between conversations and documents. (But that's just the beginning: here's the rub straight from Google). It's in limited beta right now, but you can request an invitation to be a tester.
Potentially relevant aside, also from Asha:
You could do something similar with Google Documents. (You'll need a free Google account to be able to use any of these apps.) Create new documents with menu plans, shopping lists, and whatever else the group needs to know. Then share the documents with your family. People can make changes at will. If you want to see how the documents have changed over time (such as when you added Brussels sprouts to the shopping list and they later mysteriously disappeared), in Google Docs, choose File >> See revision history. It'll all be there in black and white.