I really like the Sonos system of wireless music servers and speakers. I also can't afford it due to a wretched and unshakeable habit of collecting novelty egg cups. But my job does give me a paper-thin excuse for buying tons of Android devices, and it just so happens that a new app will let me cobble those together to make a vague approximation of a connected music system.
SoundSeeder is more or less a straight-up copy of Samsung's Group Play, with the obvious addition that you don't need Samsung hardware at either end to use it. Open up the music player on your host device and make sure that all your Android gadgets are connected to the same WiFi network. Then you can stream the audio and track information to phones or tablets running the companion SoundSeeder Speaker app. It takes a little setting up, but once you've got it all connected, you should be able to send audio to any Android device and control playback, volume, and connections via the host device.
Of course, putting all this together to listen through tiny mobile speakers is a bit pointless, so it's best to connect the satellite devices to speakers of some kind. It's also a bit of a downer that you can only listen to music stored locally on the host device through the app itself, so there's no way to stream Google Play Music or Pandora around the house. But for a quick and dirty solution, it's not bad, and the developer seems to be updating quickly. SoundSeeder is free to download in demo mode, but costs just shy of $4 to unlock for unlimited play.