Update 12/22/2012 - now (maybe always), tools like gcc are not installed by default, so you either need to install xcode from the App Store. You also have the option of installing only the command line tools from here:
(or at least these items were found in my /usr/bin/, although they may not be the latest versions)
ant
apt
autoconf
bzip2
gcc, g++
gzip
hexdump
java, javac and jikes
make
php (CLI)
tar
tidy
units
unzip