.NET technology on Linux or a good substitution?

Hello SuSE folkz, Could somebody tell me please if it's possible to run M$ .NET web applications on Linux platform? If it isn't possible, what Open Source environment can be used instead of .NET with the same or better features? One of our managers - M$ addicted drone, insists on using ..NET with ISII on WinXP platform instead of FastCGI, Apache MySQL on Linux. What arguments can I give him to go with the Open Source web environment? By the way, is it right info, or just a rumour, that M$ quit promoting .NET 'cause lack of interest and compatibility with web standards? Thank you in advance for any information. Alex