I think, powershell is the best way to do configurations you have to do once. Adding some links to global (top) navigation is one of them:

asnp microsoft.sharepoint.powershell
$w = get-spweb http://takana
$l = New-Object Microsoft.SharePoint.Navigation.SPNavigationNode("Smells like team spirit", "/pages/teamspirit.aspx")
$w.Navigation.TopNavigationBar.AddAsLast($l)

Feature receiver

The alternative is to create a web scoped feature and provide properties:

public override void FeatureActivated(SPFeatureReceiverProperties properties)
{
    var web = properties.Feature.Parent as SPWeb;
    var prop = properties.Feature.Properties\["MyGlobalLinks"\];
    var links = prop.Value.Split(new\[\] { ";#" },
               StringSplitOptions.RemoveEmptyEntries);
    foreach (var item in links)
    {
        var newLink = item.Split(new\[\] { ";" },
                            StringSplitOptions.RemoveEmptyEntries);
        var newMenuItem =
                new SPNavigationNode(newLink\[0\], newLink\[1\]);
        web.Navigation.TopNavigationBar.AddAsLast(newMenuItem);
    }
}
```This feature can be prefereably hidden. The properties are passed in onet:

NavBarLink

I found even a third way to add links to global navigation: NavBarLink