If you are running on an Intel Core 2 Duo you can double the speed of your builds by changing the Macports config option located here:
/opt/local/etc/macports/macports.conf
# Number of simultaneous make jobs (commands) to use when building ports
buildmakejobs 2
I was kicking myself when I discovered this AFTER I rebuilt gcc 😉
This option will allow you to use both cpu’s for building packages.