It's a way for you to create lists of anything you like and store them on a central place. You can invite others to participate in your lists, and you can publish them to the web or an RSS feed.
In the Listas Community Section, you will find a number of highlights of the most popular and random items from around the community of public lists such as the most used tags, the hottest lists, and prolific contributors. You can even add others’ lists (or any RSS feed) to your own Listas so you are always up to date.
You could keep a real time grocery list online, invite family members to add to it, and subscribe to it on your phone. You could use it as a to-do list and feed it into your Sidebar using a PopFly RSS block.
You can even create lists from all the things you find on the web, like search results, wish lists, videos, or all or part of virtually any page with the Listas Toolbar for Internet Explorer.
You can also watch a Demo of the same from Raj of Live Labs, courtesy 10.