In the past, Novell’s Mono Tools for Visual Studio only supported the company’s own Linux distribution, SUSE. However, recent releases have added support for RedHat, and now version 2.0 makes it easy for .Net developers to create apps for the iPhone. Future versions promise Android support as well.
Although the core Mono project is open source, Mono Tools for Visual Studio is available under a commercial license which starts at $99 for the individual version.