Got a brilliant concept for a new Internet application? Forget it. All the good ideas are taken. But for cell phones and other mobile devices, an apps gold rush is under way. "You can get a simple app made for $500 and make $5,000 from downloads, says Sam Shaw, CEO of a software development company. "If you do that 10 times it's a bit of a jackpot." The New York Times says gold-rush fever has hit iPhone developers in particular, but says prospectors may have this territory all staked up.