If you don’t have an Apple TV, you can’t use AirPlay Mirroring, right? Actually, you can — as long you have a Raspberry Pi.
If you haven’t heard of a Raspberry Pi before, it’s a dirt-cheap ($35!) micro-controller that’s custom-designed to be something of a hacker’s playground. (For just a hint of what you can do with a Raspberry Pi, check out Cult of Mac’s previous how-to, “5 hot Raspberry Pi projects for Mac geeks.”)