Links from a friend in the biz: "How to Design a Good API & Why It Matters", presentation by Joshua Block, Principal Engineer at Google, and designer of numerous Java platform features.
video: http://www.infoq.com/presentations/effective-api-design
slides w/o video: http://lcsd05.cs.tamu.edu/slides/keynote.pdf
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This is a very nice presentation for all developers or anyone that uses or follows APIs.