Maybe it's silly, but I'm pretty happy with the $5 USB lamp I got from Amazon [1]. When I'm at my desk, it's plugged into the USB hub on my overhead shelf, illuminating my whole desk; when I'm at my workbench I plug it into a USB port on my 3D printer. I've debated getting a "real" desk lamp but I get so much use out of that stupid little thing that I can't justify it.
[1] http://www.amazon.com/Super-Bright-Laptop-Light-Black/dp/B00...