Last fall, some unusual job listings began cropping up on Google's (GOOG) website. Amid the requests for programmers and engineers were postings for bond traders and portfolio analysts. By spring, tech blogs were speculating about what was going on at Google.

The answer was very un-Silicon Valley. Google, it turns out, has launched a trading floor to manage its $26.5 billion in cash and short-term investments. The hoard is the third-biggest cash pile among U.S. tech companies, after Microsoft (MSFT) and Cisco's (CSCO).