FreeAgent API - Developers

From their site: The FreeAgent API provides secure programmatic access to the FreeAgent service, allowing you to build cool and useful tools and services on top. You can access FreeAgent data, such as Company, Clients, Projects, Tasks, Invoices, Invoice Items, Timeslips, Users, and Expenses. FreeAgent is a streamlined money management tool for busy freelancers. It takes care of your money, letting you get on with running your business.