Here's another quickie for you from CES. I've seen a few physical amplification attempts, some good, some bad. The megaPhone from iSimple sort of sits in-between. It's a little rubbery megaphone for your iPhone which provides some acoustic amplification of your iPhone's tiny speaker. There's a port for the sync cable, and you can use it in portrait or landscape position.
How does it work? About as well as you might imagine. Enough to boost the sound a bit, but not so much that it'll fill the room or anything. Still, it's small (basically you can squish it) and if you need a bit of a boost in your audio without resorting to something like this, the megaPhone may be worth the $14.95 to you. I could see using this to placate the kiddos while waiting for food at a noisy restaurant, and I'm sure there are plenty of other uses for it.