A little while back I saw a post referencing a semi-hack that Gino was working the bugs out of before getting it manufactured. What? A nifty little device that can be screwed into any 5mm braze-on and will hold most lights that go on handlebars. Head over to Gino's blog for the details on why it's better to keep your light low.
I love the look of these and will probably pick up a few for my touring bike. Since it is being equipped for loaded touring handlebar space will be at a premium and I don't really see where I would put a light. One option is to add a secondary bar, but since I have a front rack with a top platform, any light mounted behind the rack might get blocked. Having the lights down on the fork avoids that problem nicely.
(The pic is Gino's, but it's pretty close to what I'm looking for)
Over at EcoVelo last week was a great post on the lack of lighting on many commuters. Short, to the point, and even including some statistical analysis (for people who like that sort of thing). The point is: if you ride in the dim, dusk, or dark you need lights. If you're riding through well-lit areas go with the blinky/steady combo to make yourself visible (blikies to attract the eye, steady to give something to focus on). If your ride is darker, go with something high powered to give enough light to see the road by.