Below is an excellent presentation that one of my peers informed me of.  Please visit the following link below to watch the presentation on how to design a good api.

http://www.infoq.com/presentations/effective-api-design

Below is a summary from the link below that describe a little bit of background on the presentation and presentor.

"Summary
A well-written API can be a great asset to the organization that wrote it and to all that use it. Given the importance of good API design, surprisingly little has been written on the subject. In this talk (recorded at Javapolis), Java library designer Joshua Bloch teaches how to design good APIs, with many examples of what good and bad APIs look like.

Bio
Joshua Bloch is a Principal Engineer at Google. He led the design and implementation of numerous Java platform features, including the Java Collections Framework. He is the author of the Jolt Award-winning book Effective Java. He holds a Ph.D. in Computer Science from Carnegie-Mellon University and a B.S. in Computer Science from Columbia. "

Reference - http://www.infoq.com/presentations/effective-api-design