If extreme portability is not your biggest concern then anyone looking for a nice headphone splitter and amplifier should head over to the Boostaroo website. Even though the Revolution is nearly as big as the iPod Nano (if not bigger) it makes up for its size with functionality.
Not only does it allow two people to enjoy the sound coming from an MP3, DVD or CD player (or anything with a standard headphone jack) but each listener has the option of cranking the volume up some 400%. So in 30 years when you head off to the otolaryngologist for a hearing aid you’ll at least have someone to go with. I also want to note that the Revolution requires 2 AAAA battery cells which only provide about 22 hours of battery life which could be a problem for some.
The Boostaroo Revolution is available on their website for $49.99 and at the moment also comes with two sets of volume control headphones.