Some people use Carbon Copy Cloner. Check
http://www.versiontracker.com for that.
Otherwise and I think that it might be either included with the Apple system, or a free download perhaps, much faster, but requires you to use the terminal imageJaguar
It's so much better than CCC, it's in beta form, but I've been told by Apple reps that the only reason it still has beta status is because they want to eventually add a GUI. I would say that imageJaguar would be first choice, especially if you are cloning to multiple machines. I did a 24 computer eMac lab in one day at about 20-25 mins per machine with an uncompressed clone size of nearly 3GB.