Screenshots

Games

OpenRA
A modern cross-platform reimplementation of the Command & Conquer: Red Alert engine using ICSharpCode.SharpZipLib, OpenTK, SDL2#, SharpFont and Mono.NAT.
OpenRA
Second Life
Second Life uses Mono as an engine that accelerates the execution of user provided scripts by translating LSL scripts into ECMA CIL bytecodes and in turn letting Mono turn that into x86 machine code.
Second Life

Gtk# Applications

Banshee
Banshee is a music organizational and playback tool.
Banshee Banshee
F-Spot
F-Spot is a photo management application for the GNOME desktop.
F-Spot F-Spot
GNOME Do
GNOME Do is a crazy-delicious launcher tool that makes performing common tasks on your computer simple and efficient.
GNOME Do GNOME Do
MonoDevelop
MonoDevelop is a free GNOME IDE primarily designed for C# and other .NET languages.
MonoDevelop MonoDevelop
MonoUML
MonoUML is a CASE tool designed for allowing all UNIX/Linux developers faster computer systems design using a friendly GUI application.

OpenVPN-Admin
OpenVPN-Admin is a GUI for OpenVPN that runs under Linux and Windows.
MonoUML OpenVPN-Admin
Pinta
Pinta is a paint program designed for simplicity and ease of use. It is modeled after Paint.Net.
Pinta Pinta
Tomboy
Tomboy is a desktop note-taking application for Linux and Unix. Simple and easy to use, but with potential to help you organize the ideas and information you deal with every day.
Tomboy Tomboy
Smuxi
Smuxi is a flexible open-source cross-platform IRC client for the GNOME desktop.
Smuxi Smuxi

Winforms Applications

Open Source Applications

NClass
NClass is a UML modeling application written in C#.

Paint.NET
Paint.Net hasn't been fully ported to Mono yet (due to p/invokes), but we can still see it using the new 2.0 controls.
NClass Paint.NET
SharpChess
SharpChess is a free computer application that enables you to play chess against the computer.

Reversi
Reversi is a popular game that is fun, requires just a few basic elements and has simple rules.
SharpChess Reversi
MonoCalendar
MonoCalendar is an application designed for easy management of calendars.
MonoCalendar MonoCalendar
NUnit
NUnit is a unit testing framework that is open source written in C#.
NUnit NUnit
MoMA
MoMA is a tool that helps you identify issues you may have when porting your .Net application to Mono.
MoMA MoMA

Commercial Applications

Plastic SCM
Codice Plastic SCM - Commercial, Cross-Platform Source Control Management system for Windows (not pictured), Linux, and Mac OS X.
Plastic on Linux Plastic on OS X
Likewise
Likewise Administrative Console (LAC) - commercial, cross-platform graphical administration console for Windows (not pictured), Linux, and Mac OS X.
Likewise on Linux Likewise on OS X
Nu Tech Software Solutions
A virtual keypad and graphical status for Ademco Honeywell alarms.

Client-server socket support, write custom modules with supplied API and examples to perform your own tasks upon alarm events, customize your own buttons and images and much more.

NuTech on Linux NuTech on Linux

ASP.NET

mojoPortal
mojoPortal is an open source content management system and web site framework portal for .NET on Windows or Mono on Linux and Mac OS X.

BlogEngine.NET
An innovative open source blogging platform developed with ASP.NET 2.0.
mojoPortal BlogEngine.NET
SplendidCRM
SplendidCRM was built on the Microsoft technology stack using Visual Studio 2005 Professional, but also runs on Mono.

Graffiti CMS
Graffiti CMS allows you to quickly publish and maintain dynamic content Web sites with little or no knowledge of Web programming.
SplendidCRM Graffiti CMS

Other Mono Applications

Unity
Game Development Tool implemented using Mono.
Unity3d on OS X
Maemo
Mono can be run on embedded devices like the Nokia 770. A video of the Nokia 770 running Gtk# is available here.
Maemo
Eclipse
Eclipse is an IDE written in Java. It can run on Mono using IKVM, the Java VM for .Net.
Eclipse on IKVM