(MONEY Magazine) – Forget The Bourne Supremacy or Spider-Man 2. The most anticipated opening of this summer is on the stock market. We're talking about the initial public offering of Web search wunderkind Google (GOOG), set for August. Its target share price of $108 to $135 would give the company a total value between $29 billion and $36 billion. These are wild numbers: By the time General Electric reached a $36 billion market capitalization, it boasted $28 billion in revenue. Five-year-old Google generated $1.5 billion last year.

Internet Mania, Part 2, isn't limited to Google. Even after a sharp sell-off in July, eBay (EBAY) is up 46% over the past 12 months, and Yahoo (YHOO) is up 88%.

Here we go again, you might be saying. But there is something different this time around. For a start, these companies have profits. And the Web business model has changed dramatically. The late 1990s was an era of specialty retailers. Amazon (AMZN) sold books, and Pets.com wanted to be the Amazon of pet supplies. Most of those companies didn't survive. The ones that did became something new: vast electronic shopping malls.

Amazon, eBay, Yahoo and now Google--call them the Net Four--are largely in the same business these days. They all connect consumers to a world of retailers, from mom-and-pop shops to big-name stores. Yahooers buy more than $4 billion worth of stuff a year using that website, and Google has a new search offering designed specifically for shopping. Ebay, the auction site, increasingly sells new merchandise that you can buy at a set price. And Amazon, in turn, is selling more used items. Go to any of the Net Four and in just a few clicks you can buy everything from digital cameras to antique armchairs. And along the way, the website gets a cut.

The stock prices are still scary. At $122, the midpoint of its IPO range, Google would cost 170 times its earnings over the past year. The typical S&P 500 stock has a P/E under 20. "I don't know how you can sleep at night and own these stocks," says hedge fund manager Bill Fleckenstein.

But if you have a place in your portfolio for a speculative play, there is a case for some of these stocks. Bill Miller, whose Legg Mason Value fund has beaten the market 13 years in a row, owns Amazon, eBay and Yahoo, and he told MONEY in July that he planned to bid on Google too. What draws him to Internet stocks is their high margins--that is, the portion of their revenue that turns into profits. Combine high margins with Net companies' fast sales growth and you could get explosive earnings.

Of course, you don't have the millions to invest that Miller does. If you decide to dive in, you need to carefully select the players with the best combination of growth and reasonable--well, relatively reasonable--valuation. Below is our take on each of the Net Four.