Matias Folding Keyboard
Not much needs be said about the Matias Folding Keyboard: it folds. It is not wireless, but USB. It will cost $60 when released next month. It weighs just under a pound.
It actually seems like a good time for another folding keyboard to show up, although it's funny that folding full-sized keyboards are now being sold as accessories for tiny laptops, which have taken the role once filled by PDAs.
Product Page [Matias.ca via Crave.CNET.com]

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The keyboard shown here which only folds in half seems downright primitive in comparison to the awesome palm keyboards that folded in fourths.
I still have my old palm folding keyboard in a box somewhere. I haven't used a palm in years but I don't have the heart to throw away such a lovely piece of tech. Hopefully someone will figure out a way to interface my iPhone with it.
The Palm keyboards were awesome.
I have them all and I love them.
They were actually made by a company called Think Outside, which was recently bought by another company called Mobility Electronics. They still sell them, but now they're Bluetooth and go for between $130 and $150 depending on the model.