Is the IPO drought over? Not quite. But OpenTable’s successful IPO today will give tech startups and VCs a sign of hope that you can still go public eventually if you have a real business. On a day when the Nasdaq is down 2 percent, OpenTable is up 40 45 percent from its offering price of $20 (which itself kept moving up from $12 to $14 initially). The stock opened at $24, and was trading at around $28 $29 last time I checked. With 21.6 million shares outstanding, that gives OpenTable a market capitalization of $605 $626 million on its first day of trading. (The company itself cleared $60 million in the offering). Update: The stock closed at $31.89, up 59 percent from the offering price, giving the company a market cap of $689 million at the end of the trading day.

This is an extremely healthy IPO. Opentable is not a blowout Internet company. But it is a solid Internet company that matters. It pulled in $55.8 million in revenues last year and a net loss of $1 million (largely due to expansion-related costs). In the first quarter of 2009, it managed to turn a net profit of $366,000 on revenues of $16 million. (For a deeper financial analysis, see this earlier post).

OpenTable delivers reservation management software to restaurants through a Web browser and collects monthly subscription revenues. In that sense it is in the same class of software companies as Salesforce—selling software as a service over the Web to business customers. But it also has a friendly (free) consumer-facing side. It is yet another example of enterprise and consumer apps merging in the cloud.

So what does it take for a tech company to IPO these days? If OpenTable is the new measuring stick, a company needs at least $50 million in revenues, have at least one quarter of profits, customers with proven loyalty, and solid growth potential. In other words, it needs to be a real business.