What you looking for is called as 'Content managing System'. It is of different types such as blogs, portals, wikis, etc.
There are MANY free and open source CMS products available. What is the purpose of using the CMS in your case? If you wish run onlike like Wikipedia, then you can have a look at MediaWiki *www.mediawiki.org/wiki/MediaWiki
If you want a detailed comparison and a demo, you can look at *www.opensourcecms.com/
And ya, even if you like ASP.net, try avoiding it unless you absolutely need to hack the scripts, modify them and all, only if you have very advanced skills in ASP.net. The overhead of ASP.net is also high compared to Linux servers!