Why not app based? My wife and I use Cozi's app on our phones and website on our PCs... http://www.cozi.com. App is free with ads, or pay for premium features ad-free.
I'm going to go with the trend and suggest an app. First, yeah Evernote is awesome. My wife and I use it to share stuff and I also use it to share stuff with co-workers(separately of course), and to sync stuff onto my laptop. Very effective app. It doesn't really
But to speak to your particular question, we use an app called Grocery Smart, available for Andriod and for iwhatever. You can set up a shopping list and when you update it on your phone because you bought something or added something, it will automatically sync with her device and update the list. So you don't buy things twice and you get updates to what you need to pick up while your there. When you start up Grocery Smart on your device, you hit the sync button (it can probably do kit automatically but it's just a habit now, so I haven't looked) It's really simple to use, and works great. We use it all the time.
Jon
But can you both edit? We used it for a while bit didn't like the fact we couldn't edit a shared note.
https://evernote.com/premium/