wol program sends a Wake on LAN magic packet to a specified computer. If the machine (and router in between) is configured correctly, the machine will start up!
The executable can be used as such:
$ wol mymachine.example.com 00:1a:92:59:97:2f
The current version of wol is 0.1.2 and is available on Hackage.
Using cabal-install, the package can be installed like so:
cabal update cabal install wol