[From MSDN Blogs]
Session Monitor is not a new tool, but it did stop working with SQL Server 2005. So I think that a lot of people stopped using it, which is a shame. The things that were broken now work again, and I would recommend anyone with any kind of blocking problems to implement this tool. With this post I hope to get some people to use it again, and to provide a new tool to anyone who did not know it exists.