Do you have a second Mac and a FireWire cable? If you do you can connect the two systems together setting up your old system in Target mode. With the second system have the new HD connected via FireWire or USB adapter or case so you can then use the OS's copy function.
You can also use Time Machine making a backup copy of your drive and then restore it to your new HD. Doing it this way you can install a fresh copy of your OS Vs an image of your old.
There are a few cloning apps out there as well like Carbon Copy Cloner or Super Duper both will cost you to get the better versions and you still end up needing to address the hardware setup to connect your new HD (see above).