As a developer, you can figure out how to make your program connect to Facebook, Twitter, SMS, and Email. Or you can use the Embarke API and connect just to Embarke, a messaging platform that connects you to them all. You can skip learning the specifics of how to connect to each of them. The REST API's website has a five minute tutorial video on how to use this gateway to its developer tools for social communications.
Are you ready to let everyone know the expert you are? Start by answering questions on Twitter using Replyz, a new service built on top of the Twitter API. It looks for common question phrases and extracts those tweets to its site. That way, the question can go beyond someone's Twitter followers.
It's always exciting to see those outside the web industry using an API to improve their sites. NY Times First Look blog has a great example of what Dallas Public Library has done with the Best Sellers API.