What's a good program or website to create and share my grocery lists?

I am looking for a program or web app that I can use to keep my shopping lists on. Here’s the features that I need:

-I need to be able to share it with other members of my family. Whether we all share one logon or each have our own, we should each be able to add or edit things on the list.

-It needs to be able to keep track of lists for different stores. I have different items I need depending where I’m at. I’d like to have separate lists for grocery, drug store, Costco, Target, etc.

-It needs to be accessible on my mobile phone. I have an iPhone. My spouse has a Windows Mobile phone. There priority would be for iPhone compatibility.

-It needs to create LISTS, not TASKS. I looked at Remember the Milk, but that web service is designed around tasks. It doesn’t lend itself well to quick check-off of a grocery list.

-As mentioned in the above requirement, I want to be able to check items off my list (preferably via my iPhone) while shopping and have them synced back to the website and/or program so my family knows I’ve bought the needed items.

I’ve looked at several apps in the iPhone app store, but have yet to find one that meets all these requirements. I have also looked at listingly.com, but that site is both slow and doesn’t have all the features either.

Any ideas?