This commercial open source CRM solution (available in a free community edition or in various supported configurations starting at $40 per month) doesn't have an iPhone-specific user interface. However, we think SugarCRM is sweet for two reasons. First, the basic application is easy to deploy, customize, and use. Second, there's no need to deploy a separate mobile application. Just access the server from your iPhone's Safari browser with the standard URL; the application detects that you're logging in from a mobile device and reacts appropriately.