Top Level: Portal Site Connection

The Portal Site Connection option is useful for inserting a link into the breadcrumbs and other navigational elements, as a parent of the site you are configuring.

What this means is that when you have a Sharepoint Site, and the breadcrumbs 'top level' isn't what you want, then go to Site Actions --> Site Settings --> Modify All Site Settings --> Site Collection Administration --> Portal site connection. You will need to be at the Top Level Site Settings to get to it.

Enter the URL and a name for the Top-Top Level "site" and SharePoint will place that link as the 'parent' of all breadcrumbs in that site collection. It is very useful if you have many sites in your site collection, and some or all of them do not link back to the parent site, or your users generally view another domain address as a "parent site", when technically, they are not related at all. This can happen in many cases, but for example, if you have an umbrella company and many sub-companies have intranets of their own based on SharePoint, you can place the umbrella company's "master" intranet URL as the Portal Site Connection URL.

Another trick is to put the MYSITES as the parent URL, and viola! All links that are site-based profile links (which get out of sync real fast), will be set to go to the mysites profile page, which is more accurate and sync'd with your AD, if you are using AD as your authentication provider.