Online symbolic calculator

I was told about an interesting website today, and decided to share it with you. The website in question is an online symbolic calculator. While it cannot replace a program like Mathematica or Matlab, it is free and has a nice set of features:

This free online symbolic calculator enables you to define variables and functions as well as to evaluate expressions containing numbers in any number system from 2 (binary) over 8 (octal), 10 (decimal) and 16 (hexadecimal) to 36, roman numerals, complex numbers, intervals, variables, matrices, function calls, Boolean values (true and false) and operators (and, or, not ...), relations (e.g. greater than) and the if-then-else control structure. Comments are C-style /* */ or //.

It also looks like it is being well maintained by its creator, so it is possible that new features will be added in the future.