One of the core design philosophy's of Microsoft Dynamics CRM, and the labeling and use of this application as an xRM platform, is that the application is built with the expectation that developers will extend the functionality and teams will integrate other applications into it. This is particularly common within the world of large enterprise.
The joy of integration for the user: User's can not only see all their data in one place, they also have options to add external data into that one place! Data that is display only, window frames that peek into other applications within the same interface (like Google or Bing), data that is synchronized realtime (such as SharePoint) and in batch (like Active Directory integration) and even more derivatives of the same!
Now to a customer, the term integration can have many, many different meanings. One of the first steps for anyone when faced with the term "integration" in a project meeting is to ask for the business process. What is the true need? Visibility, modification, creation?
"systems integration is the process of linking together different computing systems and software applications physically or functionally, to act as a coordinated whole"
The key term "to act as a coordinated whole" which does not necessarily mean duplicating data between two systems nor does it imply simple. Distributed system integration is one of the most complex data coordination needs a team can face. In this mobile world, the risk that distributed data is needed on any given project, increases.
Dynamics CRM has some distributed processing built in. When you take your data offline using the Microsoft Dynamics CRM Outlook client you are stepping into the distributed world. For instance the timing of when you go back online can impact your data and the coordination and rules around this dip into distributed thought.
OK So integration is a fact of life, so what are the options?
There are some very interesting third party vendor options. Some are loved, some hated, some are loved and hated and others are well brand new and unrated.
One of the new players (at least to me) is Synchronicity Systems out of the UK. They have a product called ECHO. I would be interested in any feedback from the field on ECHO. They have niched an offering for moving an on-premise Microsoft Dynamics CRM v3, v4 or v2011 to the cloud.
Another well known player is Scribe Software.
If you are tying into DynamicsGP (Great Plains), eOne is a vendor who has deep DynamicsGP history and Dynamics CRM connecct.
and there is also always the totally custom route using SSIS or BizTalk.