Kintera has an Open API. Kintera customers and select vendors can now access an extensive and documented API to connect their applications to Kintera Sphere. From their press release:

Kintera,® Inc. (NASDAQ: KNTA) today announced that Kintera Connect™, the company's open application integration platform, is available for clients and partners to integrate directly with Kintera technology. As a result, best of breed solutions are now available through the Kintera Connect Partner Program, providing organizations with the freedom to select solutions to best meet their unique needs.

If you are looking for more information, check out:

• Kintera Connect Resource Page
• Kintera Connect API Documentation
• Upcoming Kintera Connect Webinar