We are starting to work with Kanban quite a bit, as we are finding it solves some of the challenges with "vanilla" Scrum. For some teams, post-it notes suffice, but for many others (in particular, if you need to generate reports) an electronic tool is quite helpful. We've been looking at two tools, AgileZen.com and Kanbanery.com. Both have free options, which I highly recommend trying out. Both have very nice user interfaces, with a modern, easy to use "Web 2.0" interfaces (with apologies for the "Web 2.0" reference). Both generate nice reports. Kanbanery.com offers a set of iOS clients and GitHub integration.
The thing I like best - the reports are much, much more useful for business management (cumulative flow, lead & cycle time, task distribution from Kanbanery, for example) than the traditional burn down charts. No matter how many times you try to discourage it, over and over I have seen managers focus on having each sprint draw to a "perfect close" over looking at overall flow. These electronic Kanban reports seem to draw to a better set of management focus - which makes life better for everyone.