Friends confirm the reports elsewhere on the web [a,b] that Leigh Van Valen died this Saturday in Chicago. He was 75.
Van Valen published on a wide variety of topics, but may be best known as the originator of the Ecological Species Concept and the Red Queen's Hypothesis. While it is difficult to summon authoritative information, the latter appeared in what may be the most successful self-published manuscript in the history of our field , presently cited 1402 times according to Google Scholar.
One of my personal favorites, for its vision and clarity, was his paper on clade selection . It was virtually ignored until very recently, but it will likely receive a renewed look in view of recent developments [e.g., 3].
 Van Valen, L. 1973. A new evolutionary law. Evolutionary Theory 1:1-30.
 Van Valen, L. 1975. Group selection, sex, and fossils. Evolution 29:87-94.
 FitzJohn, R. G. 2010. Quantitative traits and diversification. Systematic Biology (in press) doi:10.1093/sysbio/syq053.
 Photo Source 'e&e': http://picasaweb.google.com/ecolevo.students/DirectoryPicsFaculty