Tvex:
Okay, here's the problem. I got my Arduino for Christmas, and I'm not even Twelve yet, so I don't have access to vast sums for resistors, LEDs and stuff. Can you recommend a 20 Dollar project?
You said you already had a bag of LEDs, which is great. You definitely need resistors to control the current through those LEDs. Perhaps you already have some, if those LEDs came in a kit. Otherwise, you would need to buy some. Fortunately they're relatively cheap. It's usually cheaper to buy a bag full rather than singly, and £5 - £6 would usually get you several hundred resistors.