When the missus and I first had smart phones we thought to ourselves, there must be a better way of keeping track of shopping lists.
We tried a few solutions but the best by far was our groceries.
This is available on your computer, iphone or android (maybe others too?) and updates an online list in real time. You can have your own lists and/or shared lists, you can categorise items and you can add recipe's.
Categorising is fantastic, the first time you buy something add a category of what isle it's in, next time you go to buy it you know exactly where to go. Now that we have everything categorised we can just go to the isles we need and never miss anything or have to go back to the other end of the shop for that blasted thingee that was hiding at the bottom of the list.
Recipe's are great too, you add all the ingredients to your recipe then when you want to make that item you simply go through the ingredients and tap to add to the list.
Real time updates are invaluable - I'll go to the supermarket and the missus can add things while I'm on the way or while I'm in the shop and they appear straight away. For a bit of fun, start at opposite ends of the shop and meet in the middle, watching the items fly off both ends of the list :)
I think one of the best features is the convenience, damn, I used the last of the peanut butter - take my phone out of my pocket, tap our-groceries, type the first few letters and tap the item on the list to add it. Used the last of your at work snacks, no problem, no need to wait to get home, just update the list and the item appears by magic (amazing shopping machine aka partner, not included).
Our groceries has made things so much easier for us, shopping no longer requires a half hour "what do we need" conversation, I don't have to call before I drop in to the supermarket on the way home, it's all just there.
Awesome app, everyone should use it :)