I'm using an Epson Perfection 1650 PHOTO on my G3 system w/out any problems. I picked it up at Fry's for $50 a year or so ago. I believe PHOTO refers to the film/slide adapter being included with the scanner.

Apple has a [link|http://www.apple.com/macosx/upgrade/scanners.html|What scanners can I use?] page.

Quick search on Outpost(Fry's online store) turned up [link|http://shop4.outpost.com/product/3614275|EPSON 1260] for $50, [link|http://shop4.outpost.com/product/4181593|EPSON 1670] for $60.