MobaLiveCD adds USB drive support to Linux virtualization app
Moba 2.1 now includes support for bootable USB drives. Got a favorite distro installed on your trusty thumbdrive? Pop it in, wait for the drive to become visible in Explorer, then press the LiveUSB button in Moba. Performance is on par with that of LiveCD ISOs running under QEMU. Of course, you get the added benefit of being able to access all the apps and data you have stashed on your drive.
Performance isn't quite what you get from running live distros in VMWare or VirtualBox, but it's a decent, low-impact way to test all those distros you downloaded and planned to check out -- but never did.