I have a fairly old (I am not sure when it was bought) iMac 5,1 running OS X 10.6.8, but I just saw the free upgrade to Mavericks. It looks tempting, but I'd rather first know if my computer can handle this OS before I try to install it.
Processor: 2.16 GHz Intel Core 2 Duo
Memory: 4 GB 667 MHz DDR2 SDRAM
(I guess that covers the most relevant hardware, if something else is important I'll add it.)