I can't imagine this deal will last long, so I'm going to make it quick: the Dell Wasabi PZ310 pocket printer is on sale for $29 shipped (plus sales tax in most states).
This is a Dell-branded version of one of those zero-ink (aka ZINK) printers that made headlines last year. That means it uses, duh, zero ink; instead heating the crystals embedded in special photo paper.
Consequently, the printer itself is tiny, measuring just 0.9 inch thick by 4.8 inches long by 2.9 inches wide and weighing a mere eight ounces (with its rechargeable battery installed).
So the Wasabi can literally ride around in a pocket and churn out prints on-demand. Prints from where? Any PictBridge-compatible camera or, better yet, most Bluetooth-equipped camera phones. (See Dell's PZ310 product page for information on Bluetooth printing.)
Alas, the iPhone doesn't seem to be supported, at least according to the FAQ page, but I'm hoping there's a workaround. Why? Because I just ordered the PZ310. Had to: it was selling for $149 just a few months ago!
Also, I've seen the Polaroid version of this printer in action, and while the 2x3-inch prints aren't spectacular, it's just crazy-cool.