Just remembered too which could be useful. When the arduino is powered with a 9v battery the LED doesn't even turn on, but when powered through USB it's brighter, but still pretty dim. I know the USB supplies more current, but with only one LED this shouldn't make a difference =/
Should I connect the Emitter to both the Power Supply Ground and the Arduino Ground??
When I reach higher currents, the transistors I have will need a bigger current to switch on than the Arduino can supply correct?
Is it still worthwhile to switch over to MOSFETs?