While this wiki is all about SPSS, many of the contributors and users of the site look forward to a day where a reliable and adaptable [open source] [GUI] general statistical package is available to replace it. There are a number of open source solutions available for particular purposes, but the two general purpose front-runners for the title are OpenStat4 (http://www.statprograms4u.com ) and R GUI (http://www.sciviews.org/_rgui/).
PSPP is a free replacement for SPSS. Nearly all SPSS syntax will work with PSPP and the windows, the dialogs and the output reports are almost identical. Some statistical procedures are not yet supported, but these are under development. Despite that, PSPP is in many instances a viable Free alternative to SPSS. Users who are familiar with SPSS, but don't want to pay the high prices, can download PSPP at no cost.
Like spss, early versions had only a command line interface, however today it is a fully featured system with its own language processor, database engine and windowing system. The current version can perform anova, t-test, factor analysis, non-parametric tests, and all the normal spss data manipulation functions. There are versions available for both Windows and GNU/Linux.
gretl is a cross-platform software package for econometric analysis, written in the C programming language.
R (GUI Project)Edit
R can open an SPSS file (after loading 'foreign' package) and can do more statistics than SPSS. It does have a fairly steep learning curve though.
If you would like to add a review of either of these programs, or add other programs to this page, just click edit.open spss windows
PAST is a free, easy-to-use data analysis package originally aimed at paleontology but now also popular in many other fields.
SOFA is a statistics, analysis, and reporting program with an emphasis on ease of use, learn as you go, and beautiful output.
Sage Notebook Use Sage, Python, R, Octave, and most other mathematical software with any web browser.