Salesforce.com: The company's software suite is now available on the iPhone. Customers can check the status of sales efforts or inventory from anywhere, at a cost of $50 per user.
TD Ameritrade: The online stock broker hired an Argentine developer to create its mobile software—and paid nothing upfront. Instead, the developer gets a cut of commissions from trades using its program.
Pelago: Its software lets you see on an iPhone what friends think of nearby restaurants or hotels. The company just scrapped plans to adapt Pelago for other phones because of Apple's success.
Tapulous: More than 5.5 million people have downloaded this game, which tests iPhone owners' ability to tap to the beat of the music. The startup turned a profit in December, six months ahead of schedule.