Not with Parallels (as far as I know), but I am running Mac OS 9 using SheepShaver for Mac Intel. You can find out more at http://sheepshaver.cebix.net/ -- it's a JIT PowerMac - free and open source software. I'm also running really old 68k software using Basilisk II - http://basilisk.cebix.net/ These are the best ways I have found to run Classic software that won't normally run on OS X Intel.
In addition - if you want to run Mac OS X in virtualization, the only app I know of is Mac-on-Linux and Mac-on-Mac, but both of these free open source projects only run on PowerPC chips at the moment: http://maconmac.bastix.net/ (for PowerPC Macs, see screenshots) http://www.maconlinux.org/ (for Macs with Linux installed) I hope one of these gets ported/updated/evolves into something that runs on Mac Intel soon! We shall see.
I remember reading that some people managed to install OS X on VMware virtual machines in Windows using "Hackintosh" installers and was hoping it was possible with Parallels... Guess not...
