You will find a shortcut to presentation service in case of OBIEE 10g in the Start menu-All Programs-Oracle Business Intelligence folder.
In case of Oracle 11g - The front end page will open by itself once the OBI services are started successfully.
In order to open the web logic console or enterprise manager we manually have to type the URL.
I took 2 copies of the shortcut of Presentation services of OBIEE 10g and changed the names and URLs in their properties and put those in the OBIEE 11g folder.
So I can now start the console and enterprise manager from the shortcuts.