tripleboot linux windowsxp osx

Hello there,

I am a happy user of parallels desktop for Mac. Here is my problem:

I love my mac, so most of the time I want to be in OSX. I do use windows (due to work reasaon), and I increasingly use linux (for work reason).

I know we can dualboot into XP with bootcamp, and Parallels can also boot into a real windows parittion.

Ideally, I would like to triple boot into linux. But, how can I make it so that I can install linux into a USB Flash drive ? I want bring this Linux USB Flash drive so that I can boot from any computer that supports USB booting. And if parallels can also boot from this USB Flash drive as a VM.

Does anyone know what I can achieve that ?

Thanks.