When I talk to people about the Airplay, AppleTV and AirPort Express setup I use at our house (see this post for more details), I often get asked about a set of speakers people have from an old stereo/amp and up until now you always had to have a big, clunky amplifier to hook up and power those speakers.
I just saw this post on TUAW.com about Griffin's new Twenty Audio Amplifier that integrates with an Airport Express:
Wouldn't it be nice if you could grab those humongous speakers that you bought back in college and somehow hook them up to an AirPlay-enabled amp? That's the idea behind the Griffin Twenty Audio Amplifier (US$99.99), which uses your existing speakers and an old AirPort Express (not included) to let you stream music to your towers of power.
So for $99 you can buy an AirPort Express, add another $99 for the Griffin Twenty Audio Amplifier and connect your old speakers and you've got a sweet wireless stereo.