Thanks for bringing that up. Computer Vision Syndrome (Google same) can also cause killer headaches.
http://www.mdsupport.org/library/cvs.html

I sometimes get them from that, sometimes from the same muscle strain as Peter, and a host of other causes. I've gotten relief from the stress-induced cervicogenic headaches with myofascial and deep massage (depending on what's messed up at the moment, and from those and migraines with physical therapy/exercises. The real buggers are the compound headaches (two or more types of headache concurrently) or the ones I call "foolies" cuz you think it's one type and after treating it accordingly for several hours, you figure out it's another type....

A good starting point I just happened across:
http://en.wikipedia.org/wiki/NIH_cla...n_of_headaches

On a humorous note, I just recalled a discussion I had with my PCP about my migraines. After describing them in detail (from my headache log ) I noticed him staring at his computer screen for a long moment. "I'm sorry," he said, "I'm supposed to categorize your headache from this list on the system. It lists over twenty types of migraine, and yours doesn't fit any of them." I sighed and shook my head, and he suddenly exclaimed, "Ah, there it is.... 'OTHER'," as he punched the ENTER key....

Doc