My RL friend and I each have a sealed envelope tucked away in our safes. The envelope is to be opened in the event of the other's earthly demise. It contains information that one would need in order to access RL assets, the combination to the other's safe, etc ...
My envelope also contains my SL login information so that my friend can take care of my SL assets, as well as contact people on my friends list to inform them as to why I have not returned their messages.
As for my items listed on OnRez and SLX ... well, I guess they will continue to sell and place money into the SL economy. Who knows ... maybe my friend will log into my account from time to time and donate my earnings to a worthy in-world cause.
Oh, and there is a notecard in my inventory ... my memoirs that I update on a regular basis. That notecard is to be given to everyone on my friends list.