A Summary of Stephen Krashen's "Principles and Practice in Second Language Acquisition": Article from the newsletter Language Learning, by Reid Wilson.
Achievement Profile: Stephen Krashen: Interview by Robb Scott from ESL MiniConference, with a picture and extensive links.
Books by Stephen D Krashen: His official website, containing online texts of numerous books and articles.
Stephen Krashen's Theory of Second Language Acquisition: Summary of Krashen's 5 main hypotheses on this topic. In English and Portuguese.