What startups here are focusing on developing on top of .NET?
icey: I've written more C# than probably any other language, but I've never seriously considered it for anything outside of my day job. I like the language and the tools are nice, but for pure web applications I feel that there are far nicer options out there.Deploying applications on Windows is pretty easy, but there are far fewer hosting options for Windows; and the options that are out there will either give you a very locked down environment or require you to have a dedicated box.Beyond that, it's kind of a pain in the ass to do a quick edit of a file to fix something when you're on the road if you don't have all of your tools available. It's just not a big deal to make single file changes in Perl, Python or Ruby because most people don't use a full-featured IDE to edit that code and as a result files are often structured differently (which is to say generally broken up into smaller chunks).If you're thinking about starting up on the .Net stack, there's really no reason not to if that's the stack you prefer to use. Bizspark is a nice program which allows you to delay the purchase of most licenses for 3 years. Microsoft has a long history of providing nice tools for its developers as well.There are definitely some big sites out there that are using .Net as well (Loopt, Newegg, Woot), and there are tons of developers out there that are familiar with the stack.I would say if that's what you are the strongest with, and you like it, there's no real reason not to use .Net - as long as you don't mind using a proprietary stack. I haven't used Mono seriously, but I've heard good things about it. However, it's still a second-class citizen when compared to the canonical .Net stack.