got a friend selling a g3/233 wallstreet [ebay]. on the downside it's got only sixty.four megs of ram and os x requires at least a hundred and twenty.eight megs to run. fortunatley ramseeker is listing one.twenty.eight meg dimms for about twenty dollars so you should be able to max out the system [wallstreets reportedly top out at a hundred and ninety.two megs] for mere dollars more. so if you've got mac envy but can't afford an [i|ti|al]book it's a cheap option.
remember to bid early and bid often. oh, and shop smart... shop s-mart.