There's a Mac edition of the ATI Radeon 9600Pro. Look here: http://www.newegg.com/Product/Product.asp?Item=N82E16814102580
It's pretty expensive, though; I think you'd be better off saving your pennies for a Mactel, rather than pouring money into an ancient machine.
I want to move up to Tiger and iLife, etc. but see my video card isn't up to snuff. Have the original AGP 16mb ATI card. What can I put in?
Just upgraded processor to 1.4 gig and will upgrade memory to 832 soon. Can't move up to G5 or MacTel quite yet, so I am slowly keeping this one running.