Maple is a powerful computer algebra system.
Mathematica is another powerful computer algebra system.
SAS (pronounced "Sass") is one of the most comprehensive statistical analysis packages. It is used by companies all over the world to do reports, querying, data mining, forecasting, fraud and security analysis, risk analysis, as well as, statistics. The functionalities of SAS components are intended to be accessed via application programming interfaces, in the form of statements and procedures; it is not a menu-driven system. Compared to general-purpose programming languages, the SAS structure allows the user/programmer to concentrate less on the technical details of the data and how it is stored, and more on the information contained in the data. This blurs the line between user and programmer, appealing to individuals who fall more into the ‘business’ or ‘research’ area and less in the ‘information technology’ area, since SAS does not enforce (although it recommends) a structured, centralized approach to data and infrastructure management.
JMP (pronounced "Jump") is a powerful menu driven statistical package. It can easily be used to explore and visualize data. JMP provides a comprehensive set of statistical tools as well as a customizable design of experiments platform. This package which was developed by the SAS Institute is heavily used by statisticians, engineers, biologists, and geologists.
LaTeX (pronouced "lay-tech" because the "X" is a Greek letter Chi) is a mathematical typseting language. It is very commonly used by mathematicians to write any number of things that require equations, such as books manuscripts, research papers, conference presentations, exams, and even Wikipedia articles. It uses a markup language to write a .tex file, which is then compiled to make the final display version, usually a .pdf file. Almost any text editor can be used to write the .tex file, and there are a variety of editors designed specifically for LaTeX, which make compiling the final document easy. It is available for free. The best way to get started is to talk to someone who already uses it. The TeX Users Group (tug.org) has links for download.