SendStation - Products - PocketDock Line Out
This is a quite interesting product. The iPod standard analog out amplified to suit headphones. It works for speakers built for a headphone signal, such as most travel speakers. It's the wrong signal strength for a stereo system however, for that one should use the 'line out' signal from the iPod cradle (do not use the line-in for vinyl however, that's apparently an oddball standard).
This device is a more compact and less costly alternative to the cradle. It also allows an iPod to be charged with a standard 6 pin firewire cable. If you already own a Firewire cradle that's not being used, this is a real bargain at $30.
What I want in my next iPod, however, is a digital output option. Then I can bypass all the amplification and DAC issues and take advantage of digital speakers.