So that I don't ever lose this information (it was very very hard to find/figure out), here is how you should compile programs using the portaudio library on a Mac:
(YOU MUST LINK libportaudio.a TO YOUR PROJECT (obviously) )

gcc YOURPROGRAM.c libportaudio.a -framework CoreAudio -framework AudioToolbox -framework AudioUnit -framework CoreServices -o YOURPROGRAM

Not so hard to find, but I may possibly need at some point in time:
For Linux:

gcc -lrt -lasound -ljack -lpthread -o YOUR_BINARY main.c libportaudio.a

For Windows:

Good question....it's not in the documentation (kind of like how the Mac compilation info wasn't), but I'm assuming it's somewhere close to how you would do it with Linux (unless you're using MSVC++...which I won't be)