What's something useful and/or cool I can do with an old iMac G4?

I have an old iMac G4 with a 20” screen. The computer is fine, except that it needs a new hard drive. This I ~could~ do, for about $40, but the G4 is just such an old model (2002–2004) it seems rather pointless…
I’ve never used one personally, so I don’t know if they’re even worth restoring for use or not.

Any interesting/useful ideas I could use this for?
(you know, besides dragging it out to a field and just going Office Space all over its ass)

At the very least, is there a way for me to salvage the 20” screen to be used as a monitor for other computers?