People who wants to run .NET framework or webservices part of it on a standalone, self-contained environment, without going thru the hassle of getting whole Microsoft IIS server setup. There are couple of viable solutions
Use Cassini : Cassini, Microsoft's own lightweight webserver (Old day Personal webserver for ASP applications), which is light in footprint. Also check for CassiniEx
Use Mono: Mono's 's XSP or mod_mono, Best part is You can envision running Microsoft .NET on Apache, using mod_mono module plugin for Apache HTTP Server.(Neat!!..:). Irony is this plugin is suppose to be working only for Unix/Linux I guess, not for Windows.
Use Cassini On Apache: Drop Cassini on top of Apache. This is one of the wonderful ideas, because Apache can serve your Java and .NET Both. There is a true collaboration or whatever you call it as.
That makes Apache a true winner across the Architecture/Frameworks.