Simplify Media is an amazing piece of software. Once you install the client on your Mac or PC and sign up for an account, you can access whatever music and playlists are stored on that device from your iPhone. While you will be using airtime, this makes basically unlimited storage capacity accessible while on the road.
Think about it. Without syncing you can listen to that huge 80 gig library of music stored on your machine back home when you get stuck in the airport. This works with iTunes on the Mac and both iTunes and WinAmp on Windows PCs. You can then stream that music to your iPhone via WiFi, Edge, or 3G.
Additionally, if you install the client on another remote machine, you can also listen to the music from there. So say you have a big hard drive at home with tons of music, well install the client both at home and at work. Then you can listen to your entire home library while at work. Really good stuff, and the software is both simple and free. Word is that they may price the iPhone client software at $3.99 after the first 100,000 copies are distributed.
So, give Simplify Media a try – while it is still free and legal!
Note: I originally thought this would stream both music and video, but unfortunately right now it is music only. We can always hope though…