Mathematics portal: http://wims.unice.fr/wims/

Usually, the first step to take when looking for information or online
tools on the internet is to head off to google.

Well, I was looking for a matrix (which is a mathematical object)
calculator the other day, and have stumbled upon this very useful
mathematics portal: http://wims.unice.fr/wims/.

I must admit that I have not yet visited all the portions of this website.
However, I can strongly recommend their different calculators.

Finding a good, free online calculator gets quite tricky once dealing
with tasks more complicated than adding or multiplying.

Their matrix calculator and matrix multiplier, for instance, are easy
to handle, nearly bug-free, and quite comprehensive.

In the site, you will find:

• Lessons and references on various topics.
• Online calculators and plotters : numbers, functions, matrices, curves, surfaces, etc.
• Interactive exercises of various styles and levels.
• Mathematical recreations : puzzles and games.
• Virtual classes and portals to manage scored student works.
• Misc. interactive documents. 

and you can also browse the site.

Cheers!