Question: I bought a 240 GB SSD to replace the 500 GB primary HDD in my new MacBook Pro.

How do I clone the current Lion system image on my 500 GB HDD to the SSD? I want to clone the entire drive not just copy data.

I can only have either the HDD or SSD in the MacBook Pro at a time. I have an external 500 GB USB drive that can I use if necessary. I've seen suggestions on using Carbon Copy Cloner but I'm not sure how to proceed with only one disk in the MacBook Pro at a time.

Answer: 
I am using the Migration Assistant on the old hard drive to migrate the data from a Time Machine backup to the new disk. It won't work for every situation (need USB enclosure, etc) - but it looks like it will work for me.
Some SSDs makers will sell it as an upgrade kit. It includes the SSD and SATA to USB adapter. You'll need to purchase the USB adapter. Plug it in and let carbon copy cloner do the rest.