I wouldn’t recommend a used iBook. The G4 version will run — just barely —the latest version of the OS, but it’s teetering on the edge of obsolescence. Little new software will support the G4 chip.
Plus - and I say this as a die-hard Apple fan — the iBook was not their most reliable machine. They have logic board problems after a while. I got more than five years’ use out of mine, which isn’t too shabby, but a used one isn’t a great bet.
The Mac Mini is no speed demon, but it’ll get you an Intel processor, so it’ll stay current a lot longer. It’ll work with just about any monitor, and any USB keyboard and mouse you already have. They’re $599 new, and you might be able to find a used one in your price range. They all have at least a combo drive, which is a DVD reader and a CD reader/burner.
A bonus is that if you have more money for a beefier Mac later, the Mini doesn’t have to go to waste; it’s a fantastic machine to put in your entertainment center as a video/music player, and with some add-on hardware and software can even double as a DVR.
Hey! I’m writing this on an iBookG4 and I love this computer. It suits my needs just fine. I’ve had it for three years and the only problem I had with it was the DC-in board. Apple fixed it at no cost (other than the price of gas to deliver and pick up the iBook at the Apple store) this summer.
I’ve been using Mac since 86 and I’ll buy another when this one is obsolete. It’s a very reliable machine. And yes, I still use Tiger.
I also love my 5.5G video iPod. Unlike the new ones, it lets me download pictures from my digital camera.