i think the basic idea is stanby power keeps the nic on and you have to send a special packet to the mac address of the system and it should turn on.
that said, i havent gotten it to work right on one of my systems, and i know a lot of companies do not implement it right or just dont enable the feature.
if you get a linksys router with the open source firmware they usually can do it remotely, which is nice, snce you could wake your computer up remotely by exposing your router to the web or something lik ethat.