iCloud now features Find My Mac service:
With iCloud comes Find My Mac, a feature that’s essentially identical to what’s been offered for iOS devices. If you have a free iCloud account and your Mac is running OS X Lion 10.7.2 or greater, has Wi-Fi access, has a recovery partition installed (more on that later) and has been set up beforehand in the iCloud preferences, you can use Find My Mac to locate your computer anywhere in the world using either iCloud.com or the Find My iPhone app on an iOS device.