An old thread but I thought I'd contribute something with my first post. I got one of these UV nail lamps to use for solder mask film - inspired by this:
http://www.instructables.com/id/Dry-Film-Solder-Mask/It works really well. As others have mentioned, the outside two lamps are lower so I removed these to help prevent light getting under the transparency.
I tried it briefly with positive photo resist for board etching but found that the UV output was too high and a normal fluorescent worked better for this.
Fred