Miguel de Icaza announced a new project today called MonoMac, to develop apps for the Mac using Mono and C#: http://tirania.org/blog/archive/2010/Apr-19.html
In the post, he provides links to the subversion repositories, but are there any builds of it available for download?
There is no binary distribution yet. But you can build your own very quickly:
maccore module svn co http://anonsvn.mono-project.com/source/trunk/maccoremonomac module svn co http://anonsvn.mono-project.com/source/trunk/monomacmonomac folder, and type makeThe sample application (found under monomac/samples/Hello) can be launched like a standard application.
I wrote a blog post about this the other day on how to use MonoMac with the latest version of MonoDevelop 2.4, building on the great work by Michael Hutchinson. Michael's post has a link to a version of MonoDevelop 2.4 beta he has slipped the MonoMac addin into. I've pulled the addin out of his beta version and tell you how to put it into the RTM version of MonoDevelop 2.4.
Due to the stackoverflow spam prevention, I'm only able to enter one link, otherwise I would link to Michael Hutchinson's blog post.