OK here are a couple examples. used radio shack.
LEDs are diodes (duh) and as such they need a current limiting resister in series with them to limit what they can draw as they will present themselves as a short circuit when forward biased. the resister will also drop the voltage.
keep this formula in mind:
Resistance (in ohms)= Voltage (in volts) divided by Current (in amps)
so for 5v supply to get 20 ma
r = 5 / 0.02
resister= 250 ohms
5v, 30 ma
resister might be too much of a voltage drop with 5v supply so tap into 12v (if the notebook has that voltage? hmm this one may not be suitable but Ill include it anyway)
r = 12 / 0.03
resister= 400 ohms
dont worry if you cant find an exact match to the resister, use the closest one higher
in value. each LED should have its own limiting resister.