1% of ASP.NET sites running Linux
According to Netcraft: .Net finds favour in the Linux community (scroll down):
Last week the Mono project released a new version of their Linux based implementation of the Microsoft .Net development framework. Mono enjoys an almost unique relationship with Microsoft amongst open source projects. Mono project leader Miguel de Icaza and Microsoft executives frequently say complimentary things about each other, with Microsoft presumably taking the view that any thing that helps establish .Net as a common development framework is a fine thing. So far, around 1% of internet sites using ASP.Net are Linux based, but it is early days both for the Mono project and for .Net itself, and both will be hoping to grow very significantly from current levels.