I am playing around #Development.
It looks cool and easy to use.
SharpDevelopment

Gtk# 2.4 Beta1 Released has released on Mono Project Page
You can build more powerful GUI in Linux by using Mono.
Mono Project

I have used SemWeb to build a tool can read OWL. I have found a C# library. That is quite good. Performance is ok too.

Visit SemWeb.

I am playing around with Mono recently.
Mono is a software package to allow Linux to .Net.
That's quite good.
I even setup some .aspx and web services are running on Apache server.

Mono Project