edu-apps.org is an open collection of learning apps that can be used in your classes.
The apps are built on LTI which is "like Facebook apps or Google widgets, but interoperable between lots of edu tools. Learning Tools Interoperability (LTI)® is a specification developed by IMS Global Learning Consortium. The principal concept of LTI is to establish a standard way of integrating rich learning applications (often remotely hosted and provided through third-party services) with platforms like learning management systems, portals, or other educational environments. In LTI these learning applications are called Tools (delivered by Tool Providers) and the LMS, or platforms, are called Tool Consumers."