I'm using a PowerMac G5 (PPC 1.8GHz, 512 MB RAM), and the performance hit of visiting this site is negligible.
I'm guessing you have a plugin/extension running amok. Try updating your browser and OS. Also, boot FF in safe mode and compare the performance. Maybe some sort of Proxy or Internet security suite is interfering. Don't disable those, but update them/ask their support staff for a solution.
Obligatory "Maybe you'd be interested in using Opera?" *nudge nudge wink wink*
Post edited September 14, 2008 by CTLance