Jesse McGrew has created ZLR, a z-machine interpreter written in C# for .Net. The aim of ZLR is to be as fast as possible. As Jesse said in his announcement,
You can get a runtime for Windows or compile it for a compatible platform such as Mono.
Inform 7 extension authors, take note: extensions librarian Emily Short has released guidelines for writing extensions that lists best practices, such as including an example and naming all of your rules.