RGB LEDS
I have accomplished what you are looking for using:
1 x BasicATOM Pro 24 Microcontroller
1 x ULM2803 Darlington driver
? x LEDS
The B-AtomPro is a programmable controller that is fairly easy to use, it is programmed in Basic and costs around $30-40US. It has a feature that sets it apart from other similar controllers in that it has 3 hardware based PWM outputs. That means it can vary the current in about 255 levels, so you can dim 3 channels independently.. RGB
The UML2803 driver takes these 3 inputs and allows you to add a whole lotta LEDs, I daisy chain the ins/outs and have 3 channels of 1amp power for the LEDS. You could probably safely drive 30-40 LEDS from one channel. And you can just add more 2803's for more leds. You can also go the way of mosfets and transistors but I used it for it's simplicity. The 2803 is probably under $1US
I buy my leds from LSDIODES.com They are extremely cheap. High Bright Leds for $0.45US-$0.65US and they sell RGB leds for about $1.10US/Each and $2.00US Shipping pretty much worldwide I do believe. The RGB leds are nice, but hooking them up is a pain as there are 4 leads where 2 would ususally go.
I like the programmable controller becuase you can hook up switches and sensors and program the effects you like and then run the thing from a push of a button. The hardware PWM is the only way to go as Software base PWM is a pain in the butt. And the code for controls is pretty simple.
eg. Dim a channel from bright to off:
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FOR ledlevel = 0 TO 255
HPWM 10, ledlevel, 10
NEXT
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or how about brighten one channel and dim another:
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FOR ledlevel = 0 TO 255
HPWM 10, ledlevel, 10
HPWM 11, 255-ledlevel, 10
NEXT
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I have about 75 different lighting effects programmed into mine.
You can find info on the Atom at basicmicro.com
It's obviously not the cheapest way to go, but is by far one of the most simple. Have a look at Luxeon leds too, they kick butt in the bright department, but they are truly the brightest on the planet and I would put 3 luxeons against 75 normal leds any day..and that's my next project..
Resc.