Strobist is dedicated to off camera flash. They have some amazing lighting tutorials on here and even tutorials on how to DIY some lighting equipment like a gridspot, snoots, GoBos and other stuff. It's a great site if you're
interested in learning how to do some studio lighting or just learning how to use light (that's a biggie...) They have a 'course' called lighting 101 (free of course) that's very informative!
(they also have a flickr group where you can submit your pictures, but they have to be done with off camera flash)
contents below Copied from site
Lighting 101 Series
(If you start with the first one, they are linked in order to each successive lesson.)