Those of you who have been involved in standing up customer portals/communities/etc. what is an abso

 Phase 1 of our community is purely support and help desk - but are looking to future iterations.  We are currently leveraging SFDC.  I realize each portal may have different bells and whistles but what have you found successful to your customers while they engaged with your portal?  For context we are a B2B software application with 350+ customers.