You can customize the navigation in SP2010 via Site Settings > Navigation:

How would I go ahead and define a simple (!) navigation myself and deploy with via feature? I don’t really want to create a custom master page – just like I would do via the frontend: Add two links to the menu and I’m happy.
I read about a custom site map provider and using a custom xml file and reference it in the web.config, but I cannot believe it is not easier to simply modify some existing links in the global navigation and add some new ones – basically create my own menu.
Let’s go with an example:
Global Navigation
Custom Folder
Products --> lists/products
More News --> lists/morenews
Entertainment --> lists/entertainment
Another Folder
Somethingelse --> somethingelse.aspx
How would I go about and deploy this to my site and replace the global navigation?
Turns out I’m looking for the SPWeb.Navigation Property. I can easily add links to the global navigation and the quick launch by using the
AddToQuickLaunch(MSDN) method.Microsoft even has a MSDN entry for what I was looking for: Adding Links to Quick Launch.
Once you’re on track you find more information:
So now I just have to add my custom navigation via a Feature Receiver and all is fine.