In addition to a previous hint, here's some more info on remotely waking and sleeping your Mac.
Requirements:
You should check the "wake up on administrative network access" in the Energy-Saver-PrefPane
Waking up:
There are several utilities for waking up computers over the LAN. A cross-platform utility is WakeOnLAN.You'll need the MAC-address of the computer you want to wake up:
% wakeonlan XX:XX:XX:XX:XX:XXTo get the MAC-address, ssh into your OS X machine or start the Terminal and
% ifconfig -aEvery network interface is listed, the ethernet-interfaces (en0) are listed with ip-address and MAC-address.
% cd [the/path/to/SleepNow]The remote machine should sleep now.
% ./SleepNow
Mac OS X Hints
http://hints.macworld.com/article.php?story=2002061709450594