I just read a blog post that pointed out that Linux Desktop use has recently trended upwards from 0.97% to 1.41%.
I can add some personal (albeit anecdotal) notes to this observation.
For one - how about the fact that I am seeing an "Ubuntu Trinidad" group - a user group from a country that was previously snobbishly anti-Linux in a way that only a 2nd world country can be?
What I think is happening now is that it is cool to understand and use Linux. It has become how facebook was 5 years ago - before everyones' mom and grandmom got on it. I think the spread of Android is behind that. The thing to note with Android is that it enables phones that fall within the purchasing power of third world countries, whereas iPhone cannot easily do that. Now that word is out that Android is Linux, and perhaps more importantly - that Andoid supports tethering - then many people in these other countries are willing to load up Linux on a laptop, and browse the web (using their mobile hotspot).
The other (possible) trend is that people are gathering old computers in their homes. Many of these were Windows XP, which MS has abandoned, and is patently unsafe with its ancient (and increasingly non-compliant) browser. Rather than re-install Windows to attempt to restore some functionality to these machines once they have suffered from bit-rot, many users are trying Linux first (or even second). Once they have a shiny new machine running Windows, having one-or-two extra machines around running Linux can be a tremendous benefit to a household.