The R project for statistical computing
Freeware
The R Project for statistical computing
Software scripts and links
An introduction to psychometric theory with applications in R from the R Core Team
Psychometrics in R Journal of Statistical Software
Psychometric Models and Methods Patrick Mair & Reinhold Hatzinger, The Comprehensive R Archive Network (CRAN)
Statistics for the Social Sciences John Fox, the Comprehensive R Archive Network (CRAN)
Multivariate Statistics Paul Hewson, the Comprehensive R Archive Network (CRAN)