I'm quite sure I saw something published recently, but can't find it.
There are many tools for this task. The closest I'm aware of that explicitly focuses on users story management is sprint.ly.
Most issue tracking systems have plugins for this purpose too; the two that I use—Redmine and Jira—both have so-called Agile plugins for tracking user stories and managing story points, burndown charts, etc.
We use Confluence, a great tool for user stories! It works like a Wiki, but with richer UI and functionality.
Be online
Confluence can be used as an intranet and at the same time be accessed outside of the company via Internet.
Enable quick collecting of story titles
Confluence have built in macros like table of content and other useful content containers such as children display.
Enable to map/share/group the collected stories
You can filter content by users, groups, labels and tags, which is shared instantly.
Allow open discussion around stories
Every page have comments, which is threaded if there are many comments.
Enable collaboration for collecting stories and elaborating their meanings
Since it’s a Wiki, you can
Trello is the tool we use. It's a board with lists which contains cards.
User stories and sprints We write down the userstories as titles of the cards. When all user stories are collected we subdivide them onto the different lists. The lists stand for the sprints. When we begin with sprint 1, we add soms more list next to it: working on, test and done.
Working on, test and done When a ticket (card) is picked up by a team member, it's dragged to the working on list. After the ticket is ready to test by the client, the tickets is dragged to the test list. When the client approved the ticket, it will be dragged to done.
Discussion around stories A card can be opened. On the card checklists and comments can be submitted. Very useful for making a task list and keep track of the communication about a user story. Also a team member can be attached to a card so everyone can see who's working on that ticket.
And yes, our clients also use the same board (per project). This way they have a nice inside view in the project.
We've used VersionOne at Western Union Business Solutions successfully for several years. It supports all of the features you've mentioned and a lot more.
Checkout https://easybacklog.com/ it's still in beta and while it doesn't exactly hit what you're looking for it does offer a solid structure to agile user stories.
I should also say that I haven't used this for a project. I'm still trying to figure out how to help my company make the shift to agile user stories instead of big requirements docs.
