There are plenty of great resources for the indie developer to get something up and running without having to be a Rembrandt or Mozart. Graphics and sound are necessary ingredients of a game, and to quickly get started on prototyping a gaming experience there are a bunch of nifty shortcuts. Many indie developers choose to use pixel art simply because almost anyone can draw at least something. Paint.NET is a superb windows-tool for making pixel art.
When it comes to icons there are a number of free sets available. A personal favorite is game-icons.net which now have 1238 different SVG/PNG icons available.
Next up is font awesome, which also have a nifty (369) and growing set of icons. As usual open source and free as in beer.
When it comes to sound the most basic 8-bit web based generator for making awesome bling beeps and chings is the superflashbros as3sfxr. There are plenty of similar tools like bfxr that also has standalones for offline use.
Finally for more advanced sounds there is the freesound.org site which have thousands of free sounds that can be used for developing games and applications. There are so many tools out there and we would be happy to hear about your own favorite free and open source tools.