According to this PC World article on an study from IDC, the open source market is growing very rapidly!  They are expecting about 26% annual growth over each of the next 4 years.  I’m sure you already knew or suspected that open source (including Linux) was taking off in a big way, but some of your peers (or your boss) might not – so why not share the statistics?  😉  From the article…

IDC found that the open source market is in a significant stage of growth, as previous barriers to adoption fall away.

This is particularly true in the business world, where companies are waking up to the fact that open source opens up more choices and gives them something to use as a bargaining chip with proprietary software vendors.