You posted info only for a G5.
If you are running Mac OS X on your G3, nothing works on the serial ports except there is a third-party driver for ImageWriters. But if you really have a beige G3, you can install selected USB cards for about US$10 to get access to a world of USB printers, provided you are running one of the right versions of Mac OS. You can also get access to Network Printers via Ethernet.
What kinds of printers do you like? Laser Printer, Inkjet, color, black and white, portable, high volume, duplexer, photo-realistic color?
Do you have Broadband Internet access?