I come across this question all too often. I have a tentative trip to Japan scheduled for about two and a half years from now, but I need about $3,500. So needless to say, I need to work my butt off at a part time job for that kind of money. XD
You're probably not old enough for a part time job yet, but either way, there are various ways to pick up some extra cash.
You could do chores for your parents, but in my opinion, that's about as good as them just handing you the money. I would however discuss this with my parents and see where they stand on it.
Babysitting is one of the most popular and efficient ways to make money as a pre-teen and teen. You may be a little young to babysit, but this is another option you could discuss with your parents. I know the Red Cross offers babysitters training courses, and that has helped me with landing babysitting jobs a lot (It calms the parents down because you're certified and know what you're doing, lol). This is definitely one to look into. ;]
You could also go around your neighborhood and offer to mow lawns. And since the weather is changing to fall (at least in my hemisphere), you could offer to rake leaves, and later this winter shovel snow. Elderly folks are especially appreciate of this and will most likely reward you with a couple of bucks. ;]
If you can play an instrument and / or sing, you could look into doing some local gigs... not a bad idea. Gets your name out there, let's you pick up some bucks, and most musicians enjoy their work (If you're not a musician, than this probably isn't a great idea. Just throwing it out there, haha).
Getting your friends involved is a good idea, especially if they're into making some extra money as well. Think bake sales, lemonade stands, etc.
There are plenty of ways to earn some money. You just have to be creative and have fun with it. ;]
@ Ripcurl - I've never heard of a permit for having a garage sale before. o: