Just about every single project I do with Microsoft Dynamics CRM includes migrating data into CRM from other applications (ERP, Outlook, GoldMine, ACT!, Salesforce.com, Siebel, etc.), and many involve integrating other systems with CRM.
While Microsoft CRM includes two free tools for data migration (Import Data Wizard and Data Migration Manager), I have found that most jobs involving complex mappings or transformations and/or a lot of data require a more powerful and easier to use tool.
For me, that tool is Scribe Insight from Scribe Software (http://www.scribesoftware.com).
Scribe Insight really makes the job of migrating data so much easier. Not necessarily easy, as data migration is almost always a relatively complicated job, but easier than when using other tools.
Scribe Insight is also the only tool I have used to integrate other systems with Microsoft CRM (e.g., Microsoft Dynamics GP, legacy databases, websites, etc.). The console feature makes it easy to build the integration processes and monitor their status.
Pricing for Scribe Insight depends on the license type (permanent for ongoing systems integration or a temporary license for one-time data migration), as well as the components you need for systems integration (e.g., adapters for Microsoft Dynamics CRM and Dynamics GP), but it is relatively inexpensive and well worth the investment, especially when you consider how much time is saved in professional services when an experienced Scribe consultant finishes the job relatively quickly.
If you are going to implement Microsoft CRM, and you know you require data migration or systems integration, then be sure to consider Scribe Insight as your first choice. Check their website and blog for white papers and valuable posts. You can also contact me by e-mail (mcross at michaelcrossconsultant dot com) or comments on this blog.