With all the buzz surrounding Apple and the launch of its latest 'it product,' the iPad, you may not have noticed that Apple's stock has been on a run to the moon. Which is pretty much business as usual for Apple shareholders. Five years ago, AAPL was trading under $40; today it's hitting new all-time highs over $230. That's almost a six-bagger in half a decade, an incredible run for a company this size.

    What that means is that Steve Jobs' insanely great consumer-technology-products company has now become one of the most valuable businesses on the planet. Apple's market capitalization (the stock market value of this company as calculated by the number of shares outstanding times the stock price) now stands at some $211 billion, making it the fourth most valuable company in America after Exxon (XOM, Fortune 500), Microsoft (MSFT, Fortune 500), and Wal-Mart (WMT, Fortune 500).

    There are a number of intriguing points here. First, Wal-Mart is worth only $1 billion more than Apple (AAPL, Fortune 500), meaning that a few dollars shift in stock price by either company could make Apple No. 3 any time now. Then there's No. 2 on the list, Microsoft, which with a market cap of $260 billion, is comfortably ahead of Apple. Make no mistake though that Steve is well aware of that gap, and would be incredibly psyched to skip ahead of his long-time rival Bill Gates. Could that ever happen? It's impossible to say, but note that MSFT has been trading at and around $30 for a decade now. (Exxon, by the way, now worth $316 billion, looks to be out of reach for now...)

    Below Apple on the list of most valuable companies are interesting stories too. Coming in at No. 5 right beneath Apple is Warren Buffett's Berkshire Hathaway (BRKA, Fortune 500). Don't bet against that company's value growing. Then comes GE (GE, Fortune 500), and after that the ampersand stalwarts Proctor & Gamble (PG, Fortune 500) and Johnson & Johnson (JNJ, Fortune 500).

    Then at No. 9 is Apple's No. 1 Frenemy, Google (GOOG, Fortune 500), with a value of $178 billion. The company's shares now trade in the $560s after peaking in late 2007 at over $700. Apple and Google have a few things in common besides the fact that they are both Silicon Valley tech companies. They both enjoy revenue growth that far exceeds others in the top 10 -- 17% for Google and 32% for Apple -- both have $24 billion in cash, and both are debt free. Rounding out the top 10 is JPMorgan Chase (JPM, Fortune 500), which after the financial wipeout remains the sole representative from the financial sector.

    These valuations, of course, can be fleeting. In January 2000, when AOL announced it would buy Time Warner, AOL had a market cap of $163 billion. Today, AOL, recently spun off from Fortune parent company Time Warner, has a market value of $2.7 billion. And there are a million ways to slice and dice the numbers to assess valuations. Apple's stock price, for instance, could easily slip by dozens of points if the iPad, now selling some 7,000 a day in pre-order (a staggering number considering no consumer has actually used one yet!), disappoints. But of course naysayers have had a poor record lately when it comes to Apple.

    To me what's most instructive here is what these market valuations say about our economy and us. Each company has its own place, right? The most valuable company is our biggest energy source, Exxon. Microsoft makes the brains of what makes most of our PCs run. Wal-Mart is our biggest store. Berkshire, you could argue, is the best of American business, overseen by a genius. And Apple, run by another business genius, is kind of the cool future company. Its products are all about unlocking the promise of technology to make our lives more productive and more fun. Right now, Mr. Market seems to think that's a pretty powerful formula.