When you see the integration space and Microsoft's offering in this space, you would find a lot of offerings there. Sometime you might be confused about utilization of each of them based on your scenario. Here is an indepth post on Microsoft Integration technologies and hope they clarify your doubts:

http://blogs.msdn.com/irenak/archive/2006/11/29/sysk-249-choosing-the-right-microsoft-integration-technology.aspx