I wrote up a nice reply to this but I think I accidentally closed my browser without sending. Oops. In any case, I think EL wire is probably the easiest and cheapest option. There are plenty of places to buy online, I've used http://www.elbestbuy.com/
before and they were inexpensive and quick. There's also EL Tape, which might be better for what you're wanting to do- i.e. straight wide lines of blue light.
You could also use LED and get a MUCH brighter result, but it would be more involved. Tape like this
has the LED's close enough together that you don't notice the points so much. But, you'd have to do your own soldering and figure out a power source. I would go that route myself because I already know how, but if you haven't done any of this before I think the EL Tape is probably your best bet.