There is an open source effort to port .NET to Linux, PowerPC, SPARC, etc. called "Mono". It's a fairly complete effort that includes a C# compiler, debugger, ADO.NET, ASP.NET, ..., and of course the CLR (CLI).
Current version is 0.28 (pre-release). First release is planned for first quarter of 2004.
More information:
http://www.go-mono.com
Roadmap:
http://www.go-mono.com/mono-roadmap.html
FAQs about platforms:
http://www.go-mono.com/faq.html#platforms
In particular:
"Question 109: What operating systems/CPUs do you support
Mono currently runs on Linux, Windows, Solaris, FreeBSD, HP-UX and MacOS X.
There is a JIT engine available for x86 processors that can generate code and optimizations tailored for a particular CPU.
Interpreters exist for the SPARC v8, SPARC v9, Itanium, HP-PA, PowerPC and StrongARM CPUs."
