Out of game IM:
I think it would be great to not only see what friends are online from our account page but to also chat with them even when we personally are not in SL
Guest Membership:
I think SL needs a guest membership like Active Worlds has/d (?) where anyone can download and use the game but they are very limited in what they can actually do (such as no Inventory and they get a plain AV non-changeable).