To hide the link of "View All Site Content" in SharePoint, open the Master Page in SharePoint Designer and find the SPSecurityTrimmedControl element. This element contains a Div with class ms-quicklaunchheader.
The PermissionString attribute of SPSecurityTrimmedControl element determines which users can view this content. So by changing the value of this attribute to "ManageWeb", only Administrators can see this link. But by changing this value the master page becomes unghosted but this is the simplest trick to hide the link from all other users.
See this page for a list of all the possible permission string values.
