Hi Karl,
I use a Kensington 7 port hub, this has it's own power supply that provides loads of power for all the extra USB goodies that I use with my 24" intel iMac.
I plug the apple keyboard and a Microsoft Intellipoint mouse into the iMac, all rest of the USB stuff is plugged into the hub.
I've had no problems with any of my gear, Lexmark E232 Laser printer, Canon iP8500 photo printer, two card readers, external backup drive and a memory stick.
A right click of the Intellipoint mouse allows me to unmount any devices as necessary, wherever the mouse happens to be on the desktop. This solves one of Apple's 24" iMac design flaws, having to cross the huge screen diagonal, on occasion, with a two button Apple Mighty Mouse in order to unmount a device.
Message was edited by: BearsPaw