Somehow it turned into eConnect Day. Let’s start with Chris Roehrich (sorry Chris but that last name sounds like something I Scooby Do would say ) at Developing for Dynamics GP with a look at Leveraging the changes in eConnect for Microsoft Dynamics GP 2010
Leveraging the changes in eConnect for Microsoft Dynamics GP 2010 – Developing for Dynamics GP – Site Home – MSDN Blogs
Development & IntegrationPayables & ReceivablesMicrosoft & the GP EcosystemGP 2010
Archived post from 2011. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.