As found on Geeking with Greg:
Google has published slides and video from a course taught to interns during the summer of 2007.
The slides are well worth reading whether you are new to these topics or consider yourself an old pro. They cover introductory topics in distributed systems, motivate and describe MapReduce, and then discuss how to implement the PageRank algorithm and a variant on K-means clustering in parallel on a large cluster using MapReduce.