Google, Apple, Microsoft and Nokia — starting today, all four will report results for the most recent fiscal quarter. More importantly, they may offer outlooks for their respective businesses over the coming months. For while these companies are major contributors to the technology economy, they’re also bellwethers in their own sectors. And that puts them in a unique position vis-a-vis their peers: Any bad news from them and we are looking at lasting problems across the entire technology ecosystem.

Mobile: Just by virtue of its size, Nokia is a good proxy for the health of the global mobile industry. It can also tell us how some of its key suppliers, such as Texas Instruments, will fare in the months to come. Analysts are looking for the company to post fourth-quarter revenues of around 13 billion euros and a per-share profit of 0.22 euros, on average, and to unveil plans to ship between 118 million and 122 million phones. I would be paying closest attention to its margin forecasts, as well as the number of units it expects to sell in the coming month.

Consumer Computing: Similarly Apple, with everything from its laptops to its web devices, including the iPod Touch and iPhone, offers a good proxy for consumer computing. If it struggles to meet its estimates, then you know the entire consumer technology ecosystem is struggling. Analysts expect the company to report that 2.6 million Macs, more than 18 million iPods and an unknown number of iPhones were sold in its fiscal first quarter. All told, Apple is forecast to post revenue of $9.74 billion and per-share earnings of $1.39 for the latest three-month period. Personally, I’m looking forward to them pooh-poohing this whole notion of netbooks.

Software Economy: While the troubles of the PC industry are widely known, thanks to a poor report card from Intel, Microsoft is likely to provide some crucial information about the enterprise software ecosystem. Sure Windows is a big portion of its business and the Xbox is cool, but in the end, the company prints money on its Office, Windows Server and other enterprise software offerings. What Microsoft says about overall demand for these products will reveal a lot in terms of what the software business will look like in 2009. Microsoft is expected to post fiscal second-quarter sales of $17.1 billion and a profit of 49 cents a share. It’s also expected to announce, for the first time ever, a big round of layoffs.

Digital Media and Web: Given the speed with which Google has been slashing its underperforming services, cutting jobs and putting hiring freezes in place, you have to wonder if it’s trying to right-size itself for a business environment that is far worse than we all think. Industry insiders are reporting declines in search-related spending, but it isn’t clear how much Google is being impacted. The search giant is expected to report fourth-quarter sales of $4.12 billion and profits of $2.04 billion, or $4.96 a share. What will be key is the reading of their tea leaves.

[gigaom]