YouTube member DTapeProductions writes in and shares their DIY LED Light panel using LED light strips. Of course you can't exact daylight temperature, and who knows if it can be properly color corrected with filters. Outside of that, it's actually quite ingenious if you think of the price + possibilities. As mentioned in the video, these uber cheap super bright LED lights can be used for accents, instead of the use of colored gels. It would be interesting to see them finish that 1200 LED panel. [Thanks Ross]
Flexible with adhesive backing, these strips are also found in waterproof versions. They are available in a variety of colors from Red, Blue, Green, Yellow, White, and Warm White. Often found as the colorful under lighting of cars since they run at 12V. It will run you about $3-4 dollars / 1M (3ft = 60 LED count) found below.
If you're looking to make those 12V LED lights dimmable, this 12V PWM designed for LED lighting should work.
PWM Dimming Controller For LED Lights or Ribbon, 12 Volt 8 Amp, 3301
[Update] Chris drops a comment and mentions that if you're not the strong silent soldering type of guy, then there are a variety of connectors available for Flexible LED strips. Check out some of the options available below that will allow you to bend the strips, or join them directly for longer runs. All found on eBay below (click here).
Flexible LED Strip Connectors