Use dot notation to specify an object and an action, for example, $Action.Account.New
<apex:outputLink value="{!URLFOR($Action.Account.New)}"> Create New Account </apex:outputLink>
<apex:page standardController="Attachment"> <apex:outputLink value="{!URLFOR($Action.Attachment.Download, attachment.id)}"> Download Now! </apex:outputLink> </apex:page>