I'm looking for a powerful tool to study that will benefit me in the creation of a company intranet. Any suggestions?

ASP.NET is a very good option. You can also use ready made CMS applications and customize it as per your needs.

This is a very general question - I'd recommend checking out some wiki applications. Which can be on ASP.NET - I think? But .NET is a framework, for which many applications exist.

I noticed that you've put out a few posts around similar stuff - wiki is a really easy to manage tool, that is usually PHP based I think? You'd typically have that on a Linux server, with Apache and PHP4 or PHP5 modules.

If you went with a .NET solution, you should check out dotnetNuke (though you could also go with a phpNuke if you were on the Linux box I described above). Nukes and Wikis are both really common CMS type tools, and you should be able to find a lot of information on the net to help you do any required customisation.

Hope that helps.