I would donate it to the local School Lunch Program that supplies hot school lunches for dozens of children each day. Sadly, these children go to schools that are spending more and more on PCs, and NOT Mac computers, rather than on library books and a hot lunch. My check is in the mail (it actually is, since this is what my wife and I give each other for Christmas and Hanukkah, a donation to our favorite charity or non-profit organization).
2) If you can squeeze TWO hundred bucks out of your wallet? Panther -- particularily if you use an older G4, as it'll run faster and feel oh-so-smooooth!
3) If you have Panther, a multi-button pointing device, just to get Expose under your fingers, baby!
4) If you can squeeze TWO hundred bucks out of your wallet and are running an old AGP GPU that doesn't run QE, hit Clickon Mac Solutions and buy an ATI Radeon 9000 Pro for $189.00!!! That is by far the best price for that card I have found (bought one, myself).
You're asking about an uninterruptible power supply (UPS), by APC (American Power Conversion), correct?!
I just picked up the APC BE500U-CN from FutureShop, $79 +tx. Seems OK, pulled the plug and everything kept going fine (kinda eerie, actually). An LCD iMac is rated at getting 50 mins of uptime off the battery. I imagine a sleeping iMac could go for days on battery.
There is a $59 model (BE350) that gets much less uptime (20 mins, I think) but if I recall correctly it had the advantage of being able to surge protect a coaxial line (cable modem) and the one I got only does DSL (phone).
There are plenty better (and MUCH more expensive) but if all you want to do is protect your home or small office equipment from surges etc AND comfortably leave your computer(s) sleeping when not in use the 350 or 500 are great, inexpensive options. If you are serving off your Mac I think the 500 would be a bit on the low side for your needs.