i've posted about knog lights before, and have been using a set of knog frogs for quite a while now. so far they've been great: they are easy to use, i can switch them between my bikes, they are small enough to put in your pocket or bag, and they look good.
the one thing i have found is that the front light in particular eats up batteries, but i think that's just an inevitability with white led bike lights, and not just an issue with those particular ones.
i was looking at the knog range, and see that one of their designs, the boomer, is available in a rechargeable usb version. given the abundance of usb recharging opportunities for a lot of people, i think this is a great innovation, and could solve my main issue with these type's of lights.
they come in knog's usual range of silicon colours (below), and will apparently run for 12 hours in flashing mode from a full charge. great! available from knog.