Microsoft Dynamics CRM is providing ONE PLATFORM for so many different applications out there that I can't even keep up. It is built to be one and it is built to integrate so that it can display, interact, pull in and/or integrate all of your data and all of your applications.
Now that Dynamics CRM is one of your options, what are options for integrating all of your other applications? Don't get stuck with even more distributed data, leverage MCS or leverage one of the great Microsoft CRM partner resources.
A bunch of field resources put together their knowledge and released this WIKI article on Microsoft Dynamics CRM Integration and I must admit it is one of the most requested tips that I get. If you have more to add, dive in or if you just need answers take a look.