The best opensource systems for .net

Usually when I'm asked about asp.net and php, this is what I say:
"C# or VB may not be the best languages for coding, but I have no doubt visual studio is the best IDE". I have experienced many IDEs specially those of java (that are used for php too). Maybe they don't have less features than visual studio, and maybe even have many more features. But I could never feel as easy with them as I feel with visual studio. Visual stuido is the only IDE that has everything you need at hand. From this point of view, Asp.net is the best.

But php has a very great advantage. It's Opensource. Not only you don't have to pay anything to have a php development machine, the main benefit is there are many many opensource solutions already out that can easily be used by developers and make development time very short, and make it easy.

Unfortunately there are not as much opensource systems available for Asp.net and what's worse is that they were not as good as php systems. php opensource systems are really great and are constantly being better and new systems are coming out.
Installing and working with wordpress is really fun and easy, and makes you feel very good. You feel you are working with a perfect and a very beautiful system, and think everything you need is available. And the default theme is so great that you often don't want to change it, and redesigning the theme usually makes it less beautiful.
On the other hand, DotNetNuke is ugly by default, and any change in its design makes it better and more beautiful, and you often have problems installing it and working with it.

But it's different now. There have come some good opensource systems for .net that are worth considering and maybe they will soon be easily able to compete with their php equivalents.
I have worked with these systems, and they are good enough to do what users need.

weblog system

E-commerce

CMS and Portal

Forum

Wiki