We have a client that aims for an integration between Salesforce and Dynamics NAV 2009/2015 (the upgrade to 2015 being planned for later this year).
Now I know what the API on the Salesforce side looks like, but how does that work on the NAV side of things?
What integration mechanism could I use to obtain e.g. contact, account, lead information from NAV 2009/2015?
You can use Web services to read/modify Nav data. I suppose upgrade of web service based integration will go smoothly between Nav 2009 and Nav 2015.
See this answer for very basic description of possible integration how it looks from Nav side.
Other options: