Well I would probably just shoot for local selling. Start with something like Craigslist and and use eBay as a last resort. Basically a G3 with a 400MHz G4 processor is still worth less than the price of shipping it (appox $45) so people are much less likely to buy since it will drive their total bill up quite a bit. If you do have to ship it, find a large box, and wrap the thing it several layers of bubblewrap. Use the large bubbles and wrap it in about 4 layers. Then fill in the extra space with large chunks of foam or towels. The trick is to put as much solid padding between the computer and the walls of the box to avoid bouncing around. Many years ago I got my Performa 6400 off ebay and it came in a huge box that was filled with newspaper and some packing peanuts. Needless to say, all that stuff shifted during transit, and the Mac was kinda beat up.