Canonical, the company behind the massively popular Ubuntu Linux distribution, thinks that its flagship product is about to blow the operating system market wide open. Next year, founder Mark Shuttleworth believes the company "can reasonably expect Ubuntu to ship on several million devices to consumers who can reasonably expect the software experience to be comparable to those of the traditional big OSV's -- Microsoft (NASDAQ:MSFT) and Apple (NASDAQ:AAPL)."

Sounds great -- where can I buy this stock? Um, hold that thought.

So many companies, so few stocks
Swedish furniture is all the rage right now. 231 huge IKEA stores in 24 countries sold simple, sleek furnishings for a grand total of about $28 billion last year. That's 14% annual growth on top of one of the largest revenue hauls in global retailing, and this company has hardly even touched the BRIC bloc and other emerging markets yet. Where do I sign up?

But wait -- there are more. Levi Strauss remains a world leader in casual fashion, its blue jeans seemingly immune to fashion shifts. Facebook is the hottest item online, and has been for the last couple of years. Publix sports some of the fattest profit margins in the grocery store field, despite head-on competition from Wal-Mart (NYSE:WMT) Supercenters and Super Target (NYSE:TGT) stores across the Southeast.

How can I invest in these awesome companies?
That's the problem. You can't buy stock in Levi's, Facebook, IKEA, or Canonical. You can buy some Publix stock -- if you work for the company or sit on its board. Even then, the share price is set by the board (currently $19.70 per share, making for a $16.1 billion theoretical market cap) and I'd advise against trading rogue shares on the scary bulletin boards, which sport a most-recent quote of $111 per share.

You might reasonably expect Publix to file for an IPO someday, giving its insider shareholders something more than a 2% dividend yield for their loyalty. Likewise, Facebook appears to be gearing up for a public appearance, along the same track that Google (NASDAQ:GOOG) followed four years ago. But the others will probably remain an investor's dream for many years -- if not forever.

What's a Fool to do?
We'll have to make do with substitutes for these potentially wealth-producing investments. Want some Facebook? I'm quite happy to settle for Google; the leader in online cash flow looks artificially cheap today, and it has a lot of growth left in it. You could do a lot worse than an established market leader like Big G.

Instead of Publix and IKEA, you could go for another highly profitable and rapidly expanding consumer-products stock, like Hansen Natural (NASDAQ:HANS) or Apple. Those substitutes are a bit more risky than their role models, but they could prove just as profitable under the right circumstances.

You'd have to take a leap of faith to the Pink Sheets to find a worthy equivalent to Levi's in my opinion, which many of us simply won't do. But there are several investment-ready Linux businesses on the market, while Shuttleworth decides whether Ubuntu belongs on the stock market or just in a strong user community. I'd start with Red Hat (NYSE:RHT), the incumbent leader in enterprise Linux installations.

But if those substitutes just won't do, you'll have to sit back and wait for those legends and upstarts to enter the stock market. Even if they never do so, you have to appreciate the investment ideas they spark in your head. It's almost always better to invest in your second choice than to have your money growing moldy and inflation-shrunk on the sidelines while the top pick gears up for action.

Further Foolishness:

Wal-Mart and Microsoft are Motley Fool Inside Value selections. Google is a Motley Fool Rule Breakers pick. Apple is a Motley Fool Stock Advisor recommendation. Try any of our Foolish newsletters services free for 30 days.

Fool contributor Anders Bylund owns shares in Google and Hansen, but holds no other position in any of the companies discussed here. You can check out Anders' holdings if you like. Foolish disclosure can hardly wait for the Tampa IKEA to open, if only for the smorgasbord of Scandinavian delicacies in the cafeteria.