For those of you with infrequent data analysis needs, the Web 2.0 movement offers a host of free online statistical analysis options. While theses freebies may not have all the fancy additional options (although some of them really are quite elaborate), they are great for basic data analysis! Depending on your needs, there are various online packages available at the click of a button:

• The R Statistical Language The open source statistical language of choice for most tasks. 
• ADE A modular multi-variate analysis program which includes modules for spatial data analysis. Plays well with R. 
• Adamsoft A general purpose package that specialized in client-server based data management, and large-data/low memory computations. Good for large datasets. 
• DataPlot A powerful, but somewhat byzantine package from the National Institute of Standards OSS
• Gretl An open source econometrics package that plays nicely with R.
• ExaStat Basic statistics and regression on large data, using Windows. 
• Macanova Reasonably powerful & programmable, if not easy to use. 
• OpenStat General package focusing on teaching, IRT. 
• PSPP Aspires to replace SPSS. Reads SPSS files and provides the data manipulation functions, but is missing most of the analytical features. 
• Simfit Reasonably powerful with emphasis on simulation , command-line. 
• WinIADAMS A free Windows package for exploratory analysis, time series, and linear models. Nice interactive multi-dimensional table browser and interactive plots.