Available now for US $29.95 (regularly $39.95) over at Gadgets and Gear, when not in use the "small and compact iFlash can be attached to the iPhone through a plastic 3.5mm jack and left dangling from the iPhone like a phone charm." I'm not sure a dangling charm is a big selling point, but to each their own. I would rather put that $30 or $40 towards a new iPhone that already comes with a flash -- and without a charm. If I wanted to carry an accessory for my iPhone I think I would prefer a new lens choice over a flash. But if you're stuck with an older phone and take a lot of pictures in dark places, there you go.
Back in 2007, reader Joe let us know about a DIY hack he did using LEDs and a broken iPod car charger, creating what he called the iFlash. This solution might be pricier, but it's a little more tidy, and you won't have to break a car charger to make it!