here is what i use when installing LEDs. decide how many you want, or of what color/brightness, etc... then go to this page, and you can calculate everything you could possibly dream of that has to do with LED connections and resistors.
MetkuMods - Because you love your hardware!
this is a page that describes how the leds work when hooked up in different ways, and tells you how to hook them up
LED Circuitry tutorial: how to hook up LEDs.
just some basic info for everyone who is looking at installing some LEDs easily. i always buy mine at radio shack. buy a simple switch too while you're there!