I am working in a small agile team and would like a free online Kanban board that links with TFS. The reason that I would like it to link to TFS is to cut the admin of entering in all the stories and having to update another piece of software.
You might take a look at this project on Codeplex for a WIP board that you could use in as a Kanban board. It appears to be process agnostic. It does not appear to have moved out of Beta 2 so I am not sure what the level of stability is or if it is getting any work done on it any longer. It does integrate with TFS 2010 though.
Visual WIP http://visualwip.codeplex.com/
The author is Hakan Forss and at least one blog post about the project is here: http://hakanforss.wordpress.com/2010/08/16/first-prototype-of-team-foundation-server-2010-kanban-board/
You may want to look at TFS 2012. It now has a Kanban board in the tool. There is a preview version of the TFS service in the cloud available if you want to check it out.
When I looked into it for TFS 2010, I was only able to find free Kanban tools that did not link to TFS, or paid ones like Urban Turtle that could actually integrate with TFS 2010.
Perhaps no link with TFS, but consider to use Trello: it's free and worth it!
We used to use TFS Workbench before we upgraded to TFS 2012. Its a Windows based application but used to work well.