For coders, one of the most difficult aspects of creating a game is finding the graphics and sound resources needed to bring a game to life. If you can't pay someone to produce resources for you, you'll have to either find someone willing to work with you for free, buy them pre-made, or find free resources.
Your first step should be to check out if what you want has already been made - whether it's available for free or at a price. If, for example, you're making a space shooter, you'll be in luck as there's plenty of free space ship, laser-like, and explosion graphics and sound around. Check out the list of resources below for sites that stock free and paid graphics and sound. There's a good chance you'll be satisfied with what's already out there.
If you can't find anything out there, or if you're particular with what your game needs to be just right, paying someone to create exactly what you need is the best option - assuming you've got the cash. This way you get exactly what you're after and won't have to compromise your vision.
If you're strapped for cash but can't use something off the shelf, but you have skilled graphic designer or artist friends, you might be in luck. Ask around. Otherwise, hit up game developer forums and see if you can sway a friendly internet person to help you out. There's plenty of enthusiasts who might buy into your vision and be happy to work with you for free.
Get started by checking out the many sites providing graphics and sound below.