This page lists the various (scientific) programming tools that I use, some of my reasons for using them, and some usage hints.
You can't beat gcc - it does pretty much everything, and it's free.
The standard development environment on a Mac is XCode, which comes free with the operating system.
For the maths side of things, I tend to use the GNU Scientific Library, which is full of lots of useful mathematical functions. To install as 64 bit on a mac, use ./configure CFLAGS="-arch x86_64". See GSL for usage hints.
For Fourier transforms, FFTW is good.
HEALPix can pixelize a sphere. See Healpix cxx for usage hints with the c++ version
I use cfitsio to read and write fits files in my programs.
I need to find a decent graphics output at some point... QT or OpenGL would probably be best. Allegro doesn't seem to be that good...
Doxygen - sudo ln -s /Applications/Doxygen.app/Contents/Resources/*doxygen* /usr/local/bin/doxygen is a useful command to run.
CrossVC-XXL. Need to find a better CVS gui than this at some point.
Libnova provides various astronomy-related functions. It can be compiled in 64 bit mode on an Intel Mac using (for version 0.12.1):
./configure CC="gcc -arch x86_64" CXX="G++ -arch x86_64" make make install