I use vmware workstation ... i think vmware fusion is avail for the mac...
parallels works better on the mac/ubuntu than it does on windows
but i have windows vista running vmware workstation and i tried same
experiment with parallels for windows and if your on windows vmware
workstation has ultimately proved to be more beterrer (lol) .... just have a
core 2 duo 2.4ghz(x2) and 3gb of ram and its running ubuntu 8.04 gui,
ubuntu jeos, windows xp, and windows 98 all at the same time with little
or no noticeable lag... i can watch movies, make skype calls, and do
just about whatever inside of the emulated virtual machines .... i cant get back into wow or online games i am
powerless to control my addiction to it and cant go backwards from step 12
on this one...

...my 6 monitor rig
for some reason , and i have no data to back this up but it seems the more ram i devote to some of these vms the slower they run.
@nbs: if you want, i can send you my jeos ubuntu server or anyone already set up lamped and ready to roll... just hit play and your rockin.
if anyone wants to roll their own i posted the steps i followed:
http://www.perkiset.org/forum/php/ubuntu_804_jeos_just_enough_os_lamp_server_for_dummies-t920.0.html:jealousywank.gif: that sounds so balls awesome.