Im using en AKAI EIE (red thing) with a Phonic 100w mixer (gray thing) connected to a pair of stage monitors.
With a single USB cable, I get a 4 channel input that can toggle between mic/line and direct input (or Guitar as shown on the labels)
This is great for anyone that wants to start a home recording studio on a budget. In my opinion it offers the best features and functionality for the lowest price.
It not only works as an audio interface, but offers 3 extra USB expansion ports, so you can plug anything you want to it (as long as it has USB of course!)
The EIE is great for my MacBook Air, because it offers 3 extra USB ports. When I get home, all I do is plug it in to my Mac and its gives me the functionality of a laptop dock station. I can have a mouse and keyboard, as well as a MIDI controller with and still have a spare USB port on my MacBook Air (this is awesome because it only has 2)