So I've been hearing great things about MS Dynamics CRM 3.0.  With some of the new features like clustering support and the ability to do 3rd party hosting.  Dynamics CRM is turning out to look like a very good solution for ISVs to either embed in their current product lines or rebrand and host in a SAAS model.   

Check out the GotDotNET site here:

http://codegallery.gotdotnet.com/crm    

and the MS site:

http://www.microsoft.com/dynamics/crm/using/default.mspx