Metaphorix have recently had a lot of projects which involve integration between CRM 2011 and NAV 2009 R2.
Microsoft have developed the NAV/CRM connector which is a free product to Microsoft Partners. It can take a bit of time to get used to and there are a few errors you will come up against but search this blog for answers because Metaphorix have blogged a lot about the connector and we might have a solution to your problem.
When you are going to install the connector you will need quite a few accounts created and you will need to talk to the customer and get them to create these accounts and give you the details before you can install the connector.
Below is a list of the accounts you will need, the text below is taken from the CRM/NAV connector installation guide which you can find on the partner source website here