DotNetJunkie XL on the 7th Floor

CMS: What should be in there? What do you recommend?

I have read many articles about CMS.

But what is it? What should be in there? For what do you use it?

So far I've seen some and all of them are missing essential content or content editing possibilities.
In my opinion a CMS must also give you the opportunity to inherit content of other existing sites in a control.
For example, if I have a site with a forum (built in PHP or .Net) and want to show it in a pane of my new site, then that must be possible without having problems with scripts or content display.
If I'd like to use data (xml data or feeds) from a source, then that must be easy to configure for a user. If I'd like to use a datasource (whatever databse or flat file structure) then it must be possible. If I want to change my template, then it must be easy to do so.

I don't know if there are .Net open-source content managing systems that meet my expectations... or should I just start building my own?

Give me some advice! Let me know what are the right requirements for a CMS for you guys?