No. 2: Omniture

Annual growth: 108.1%
Category: Web site analytics
Employees: 350
CEO: Josh James
Competitors: Coremetrics, WebSideStory, WebTrends

“We just paid you $100,000. What’s happening on the Web site?” Back in 1996, Josh James heard that question from customers of the Web site hosting company he’d just co-founded, fresh out of Brigham Young University. So, James and his crew built a set of tools—originally called SuperStats—to track what Web site visitors were up to.

James, 33, has since landed some big-name clients for his company, which can show activity on a Web site using myriad metrics and provides insight into how to convert online browsers into shoppers.

Its 1,300 clients include AOL, Ford, General Motors, Hewlett-Packard, Oracle, eBay, Microsoft, CNN and Wal-Mart Stores. (Disclosure: Ziff Davis Media, which publishes Baseline, is an Omniture customer.) The company runs data centers with 10,000 servers, switches and routers, capable of crunching 100 billion transactions per month.

Unlike most of the companies on our list, Omniture hasn’t made any acquisitions to double revenue year-over-year. What’s fueled the rise, says James, are the continuing growth of online advertising and e-commerce.

Omniture is losing money—it had a net loss of $17.4 million last year—but that’s by design, according to James.

“We made a decision to grow as fast as possible, because you’re going to have customers for years and years, and it’s important to become the biggest player in this space,” he says.