Samsung is the king of thin, and it just got obvious with the upcoming release (ITU Telecom world 2006) of the SGH F300 MP3 phone. It's so thin, a reviewer had trouble finding the crack from which the keypad slides out, but it turns out it's no slider but a two-faced monster with ate Moss's physique. Unbelievable? I couldn't wait for the official photos.
It is simply amazing as you can see for yourself from the annotated drawing courtesy of Slashphone (click to enlarge). The only downside I can see from the design is the phone/keypad side will have to make do with the smaller screen. The TFT screen is exclusive to the multi-media side. From this side you can listen to music (AAC, AAC+, WMA), view videos, use the camera (no idea about the resolution) and listen to FM radio. Both sides function independently of one another and will not shut down while the other is in use (much like in normal, one-sided phones).
Other fun features: screens are actually switchable, so if you want to view a picture message, you can switch to view it on the back; the battery will be built-in and replacement via service center is advised; SMS on multimedia side is possible with touch-sensitive multimedia button "dragging" over the letter of the alphabet.