I was helping a client set up his home network today. He has a mac mini which he wants to control iTunes on from his laptop. I pointed him towards coverbuddy a brilliant little piece of software that allows you to control your iTunes from anywhere using a web interface. With this in mind I decided to see if it worked on the new iPod Touch - It did!
The interface is a little small on the screen at first but that's easily sorted by zooming in.
It basically means that you can plug your mac into your stereo and control your music from the iPod. I've done it before with the PSP but got a little bored of using the little mouse pointer on the psp, but with the touch interface I can see this being quite a nice cheap alternative to Sonos.