Yes, you can use dual monitors on a G5 iMac

macparts.de/ibook :: View Forum - iMac: "The ultimate Mac screen spanning resource!"

Ok - it's not supported, and it's a hack, but folks have been using that patch for 6+ months and reporting no problems.

(Nat - checking to see if you read this thing!)

Note - the iMac G5 only has analog VGA out - your second monitor must accept analog VGA.