Software Links
I use a Mac. Much of the software below is Maconly.
Calculation

Mathematica
Unequalled platform for symbolic and numerical mathematics. A theorist's best software friend.
www.wolfram.com/

COMSOL
Powerful, easytouse platform for finiteelement solution of PDEs.
GUI for drawing problem geometry; automatic mesh generation;
menudriven specification of equations, boundary conditions, and parameters;
versatile visualization of results.
www.comsol.com/
Simulation
Programming

C++ reference pages
Excellent online reference for C/C++ language and standard libraries,
particularly including the C++ STL (Standard Template Library) containers and methods.
C++ Reference
www.cplusplus.com/reference/

Numerical Recipes in C online
Free online version of older edition of Numerical Recipes book.
Numerical Recipes in C
www.nrbook.com/a/bookcpdf.php

Python
Powerful, well designed, widely used scripting language.
Dive Into Python
http://diveintopython.org/toc/index.html
The Python Tutorial — Python v2.6.5 documentation
http://docs.python.org/tutorial/

SmartSVN
GUI for subversion, version control software for collaborative development of programs and documents.
www.syntevo.com/smartsvn/index.html
Writing

LaTeX
Tutorial and reference websites for using LaTeX,
by far the best choice for technical word processing.
WYGIBTWYT ("wiggibtawitt")  What You Get Is Better Than What You Type.

Cambridge University Engineering Department  Text Processing using LaTeX
wwwh.eng.cam.ac.uk/help/tpl/textprocessing/LaTeX_intro.html

Getting to Grips with LaTeX  LaTeX Tutorials by Andrew Roberts @ School of Computing, University of Leeds
www.andyroberts.net/misc/latex/

LaTeX  Wikibooks, collection of opencontent textbooks
http://en.wikibooks.org/wiki/LaTeX

TeXLive
Open source installation of TeX, LaTeX, TeXShop, BibDesk, LaTeXit.
TeX Live  TeX Users Group
http://www.tug.org/texlive/

BibDesk
GUI for editing and managing .bib files.
http://bibdesk.sourceforge.net/

LatexIt
GUI for using LaTeX to typeset equations to paste into Keynote, Pages, (Powerpoint, Word,...)
http://chachatelier.fr/programmation/latexit_en.php
Shareware

Macupdate
Widely used repository of shareware, freeware, demo software.
MacUpdate: Download Apple Mac Software & iPhone Software
http://macupdate.com/
Graphics
Organization
Communication