OpenStat is a powerful and free statistical package that was originally written to help in social science research.
Nowadays OpenStat has been expanded to handle all kinds of data, although the developer itself admits that it's not the "finished product" yet. This means that any results you gain from it, can't be guaranteed and should be double checked either by hand or using other software.
OpenStat, rather than just present data in graph form, attempts to test and display data in one go, meaning it cuts out the need for a separate research package. It looks remarkably simple and generally, it is easy to use but it's actually quite a complex package, able to handle all kinds of algorithms and parameters that you define. However, the developer could have put more effort into making both the interface and graphs look better. In addition, according to the forum it does have problems handling certain formulas but this is probably because it's not the finished article yet.
OpenStat is a simple to use but powerful statistical analysis and graphical display package that can handle most of what you throw at it.