We've integrated JIRA and the popular CRM - Salesforce.com. See the first plugin at Integrating JIRA with Salesforce.com.

We're looking for keen customers to help us perfect the integration to their requirements. Let us know what you think!

We've also begun hosting a wiki of FAQ's relating to Atlassian products and plugin development that our team has put together and will continue to contribute to over time. You can visit the wiki here