I've done exactly that with Windows 7 as opposed to Linux. You can add a partition to your hard drive with Disk Utility, then just boot to your Linux flash disk and install it on the second partition you created.
I'm not sure how Linux functions with Chameleon/its bootloader, so you'll have to look elsewhere for that, but this should get you started and at least get Linux installed and running. Don't worry if after you install you can't boot to your OS X partition. Unless you've overwritten your OS X install with the Linux installer, your partition and files are still there, the bootloader has just been modified by Linux so it doesn't see your OS X partition.