Hiding the SharePoint Login (or anything else)
This is one of those extremely useful little tidbits that doesn't seem to be all that well documented...
If, for instance, on a internet facing site, you want to hide the login control etc at the top of the page, just wrap the sharepoint Login div with the SPSecurityTrimmedControl tag:
<Sharepoint:SPSecurityTrimmedControl runat="Server" PermissionsString="AddAndCustomizePages">
...global links table containing the login control etc.
You can use the SPSecurityTrimmedControl to hide other content as well - any content that you don't want to display to users who don't have a specific right. The PermissionsString specifies a specific right - AddAndCustomizePages is only one possibility. All of the possible settings can be found here: