R - Not for Your Average Statistician
R is to the open source world what SAS is to the for-profit world of statistics. R is a program that is very versatile and powerful, but is not the easiest software package to learn by any stretch of the imagination. R is a statistical programming language similar to the programming language S that was originally created by Bell Laboratories. One of the important aspects of R is that it can be loaded on numerous operating systems including Windows, Mac OS, and UNIX. Most other open source statistical software packages really load on one or maybe two operating systems.
One of the fascinating aspects of R is the size of the developer network. Because R is an open source software product, statisticians around the globe have created numerous add-on packages that help individuals perform a range of important statistical tests. R can be used for both univariate and multivariate statistics, structure equation modeling, time-series analysis, and many many more tests. To learn more about R, check out the R Project Website.
R for SAS and SPSS Users
Interested in learning more about R? Robert A. Muenchens has written a book specifically designed for those of us who have experience using SAS or SPSS/PASW. This book is designed to help existing SAS and SPSS/PASW users understand the basics of the R language and how R is similar to and different from the other statistical packages.
Just want to get a quick overview of the similarities and differences between R and either SAS or SPSS/PASW, Muenchens offers a free version of this text as a sort of introduction to R. You can download the free version of R for SAS and SPSS Users by either visiting the R for SAS and SPSS Users Website or by clicking on this link.