The 5050 RGB LED strips are mounted to a peiticoat / underskirt to allow the dress to be washed, modular, and to "poof" out the dress for extra effect.  The LEDs are mounted facing inward to make a diffused glow and so the dress will not have point light sources.

For the power regular I used a super overkill cheap 240W step down buck power supply I found on amazon.  I wanted something fully enclosed, waterproof, low heat, for piece of mind against arcing or overheating.  There is probably a much better potted or fully enclosed low cost solution out there and would like to see what others recommend.  There are a ton of low cost buck regulators on ebay but I have not seen good options for ones that are potted. 

I did not want to purchase a battery just for this project so I decided to use my 18V lithium ion Ryobi power tool batteries with a 3D printed cap I found on shapeways

Full LED Dress how-to instructions from my blog