While this may not be exactly what you are looking for, I'll throw it in there anyway.
GNU Octave is an open source "clone" (of sorts) for matlab. It may not help you learn maths, but it'll maybe be of some use if and when you do matrices, it's very convenient for checking your solution or doing some of the grunt work when you are quite happy with the basics like multiplication and finding determinants and just want to get to the bits that are challenging for you, especially on 4x4 or greater matrices.
It's available for linux and windows (via cygwin). Dunno about mac's.
As for learning calculus, I'd have to agree with the other guys - camp out in the library. A book I've been using and find reasonably good for self study is Calculus a complete course by RA Adams. It works for me, though I've not read many similar books so I can't comment on it being "best".
Also, there's a good deal of stuff online if you look, here's one such resource. You could also check out the parent site, there's a lot of stuff but finding something useful and appropriate may be hit or miss for you.
http://www.freescience.info/Mathematics.php?id=343
http://www.freescience.info
First link is the calculus section.