Compiling Aircrack on 10.6 Snow Leopard

First off get it by using:
svn co http://trac.aircrack-ng.org/svn/trunk/ aircrack-ng
Now, you need to edit common.mak to build for a 32-bit architecture using 10.5 headers, and have it use gcc-4.0 instead of 4.2.
Find this line:
CC = $(TOOL_PREFIX)gcc
and replace with:
CC = $(TOOL_PREFIX)gcc-4.0
Then find this line:
CFLAGS ?= -g -W -Wall -Werror -O3 -Wno-strict-aliasing
and replace with:
CFLAGS ?= -g -W -Wall -Werror -O3 -Wno-strict-aliasing -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk
Go back to Terminal and:
cd aircrack-ng
make
sudo make install
The binaries can be found here: /usr/local/bin/

Remember you can only really use it to poke at already captured data…