"Names You Need to Know in 2011: R Data Analysis Software"
November 29, 2010
It's free and open source. I have haven't--thanks, Steve W.--used it in my classes yet, but it could well be excellent for graduate students.
Some other R-related links that may be of interest:
Where to get R and its documentation: "The Comprehensive R Archive Network".
Add-ons: "Must-Have R Packages for Social Scientists". See also "CRAN Task View: Computational Econometrics" and "CRAN Task View: Statistics for the Social Sciences".
Why R? "An economist explains: Why I use R", "R is Hot", "How Google and Facebook are using R", R-Bloggers.
Learning R: "Resources to help you learn and use R", "Quick R", "R Beginner’s Guide", "Finding my way around R"
Other: Springer books about R, R-Commander--a GUI for R, recent Fordham "Conference on Quantitative Social Science Research Using R", "Revolutions", "R Tutorial Series: Hierarchical Linear Regression".