Ok, I know resistor calculators have been posted here in the past, but I've found one that I think is a lot better, so since I'm new and want to contribute, I figured I'd share my source for picking the right resistor. LED Resistor Calculator.

Most of it looks pretty standard, but go to the bottom, to the Guru section. It will tell you the resistor to use, the layout, and will even suggest parallels circuits if you don't have a stable enough power supply for your leds. Good luck!