How to change the 'Main Page' title to something else?
The default name for the MediaWiki main page is Main Page.
To change this edit the MediaWiki:Mainpage page by going to:
http://www.yourdomain.com/index.php?title=MediaWiki:Mainpage
where yourdomain.com is your actual domain name where MediaWiki is installed.
Click on edit and change Main Page to the new page name you wish to use and save.