There's an excellent blog post by by James Nebeker and David G. Young about simulating an iBeacon using a Raspberry Pi and a bluetooth dongle. Since I already had both, I thought I'd give it a try. It worked really well, and I've even put together the files necessary to do it in my GitHub repository.
You'll need to install BlueZ as well for this to work. Once you get it all installed and working you can use one of the mobile iBeacon apps, such as iBeacon Locate. Very fun to play with, and a good way to be able to develop mobile apps to access iBeacons without having to wait for them to come out.
Also, it's just fun to play with.