Scilab - help
Maxima
Python
Octave:
Matlab & Simulink
Sage
Maple
R
Euler
Verkkosanakirja
Wikipedia: Mathematics
Wolfram MathWorld
Encycl. of Math
Stack Exchange
MacTutor History
Theorem of the day
Mathwords
ProofWiki
Mathematics
Geometric Algebra
S.O.S. Mathematics
Euclidean Space
L-systems