Octave is a free program for doing math computations, especially ones related to linear algebra. You can experiment with parts of Octave online at the following site:
http://lavica.fesb.hr/octave/octave-on-line_en.php
Some hints about using Octave can be found at Octave’s online user’s manual
Wikipedia gives some other links to Octave web-user interfaces, but it seems you would need to register with them. I have not tried them.
* http://nclab.com -NCLab Move your Octave/Matlab stuff to the cloud, share, collaborate – it’s free (virtually no restrictions).
* [http://www.verbosus.com] – Online Octave editor with plotting and storage.
* [http://www.online-utility.org/math/math_calculator.jsp ] Online access to Octave– Allows you to perform simple Octave calculations online.
* [http://www.mathcloud.se ] MathCloud– Share MATLAB/Octave scripts and data and do your computations in the cloud.
* [http://hughesbennett.co.uk/Octave ] use Octave online within a Web browser.