Sage is a different approach to mathematics software.
The Sage Notebook
With the Sage Notebook anyone can create, collaborate on, and publish interactive worksheets. In a worksheet, one can write code using Sage, Python, and other software included in Sage.
General and Advanced Pure and Applied Mathematics
Use Sage for studying calculus, elementary to very advanced number theory, cryptography, commutative algebra, group theory, graph theory, numerical and exact linear algebra, and more.
Use an Open Source Alternative
By using Sage you help to support a viable open source alternative to Magma, Maple, Mathematica, and MATLAB. Sage includes many high-quality open source math packages.
Use Most Mathematics Software from Within Sage
Sage makes it easy for you to use most mathematics software together. Sage includes GAP, GP/PARI, Maxima, and Singular, and dozens of other open packages.
Use a Mainstream Programming Language
You work with Sage using the highly regarded scripting language Python. You can write programs that combine serious mathematics with anything else.
The Sage Notebook is based upon work supported by the National Science Foundation under grants DMS-0821725, DMS-1020378, DMS-0713225, DMS-0555776, DMS-0545904, DMS-0838212, DMS-0757627, DUE-1020378, DUE-1022574, DMS-1015114, etc. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. See also http://sagemath.org/development-ack.html.