Options for playing music wirelessly from iPod touch and iPhone?

What are the options for playing music from an iPod touch over speakers in multiple rooms, preferably with the ability to turn speakers off in a specific room using a remote? I currently have a basic stereo system but it's about 5 years old, only has two speakers, and doesn't support Bluetooth so I'm not sure if it's worth trying to use with the iPod for this type of setup. Cost isn’t an issue at least until I figure out what the options are.

Today Apple announced that the upcoming iOS 4.2 update coming in November will contain a feature called AirPlay where you can stream music, video, and photos directly from your iOS device to a new Apple TV (and presumably the Airport Express).