If you're looking for heavy open source adoption, apparently the place to go is the Fatherland, at least according to this article in Heise. Citing zero licensing fees, access to source code, freedom from lock-in, and other factors, the Germans are on an open source binge:
In a survey of IT procurement officers from Germany, Great Britain, and the US/Canada, 59 percent of those in Germany said that they use OSS in their companies. The figures were far lower in Great Britain and the US/Canada at 48 and 38 percent, respectively.
Nicht schlecht! While I'm glad for Germany, I don't mind a 38% adoption rate in the US, either. Having said that, my experience is that the US pays for open source, whereas Europe does not (which would seem to be in keeping with the survey's finding that Germans like open source, at least in part, because of its $0.00 acquisition price). Still, with ~60% of German companies in the open source camp, that can't help but translate into money at some point.