Would it be a big hassle to code a message board for homeowner's doors so friends / visitors and home owners could leave notes there? It's very "college dormitory"-like, I know, but those little door message boards are very useful for neighbors and friends to know what you're up to. It's not like a mail message, which doesn't depend on your location as much.
You could detail your visiting rules ("Sorry, I won't let you in if I am not home, but feel free to leave a note or friend me so we can meet", etc.; I *think* you can use the name link at the bottom of a note to add a contact but haven't put it to the test yet) or where you plan to be in Ur for a while so lower-level friends or neighbors can find you (especially good for folks who like to mine and might want a mining buddy to boost their rock haul rewards, or who have a key to a special area and would be glad to let newbies follow them into it), or "wanted: trade / buy" notes, or "please feed my animals" notes (for friends with access, if that is coded, while you are offline), planned party information, personal quirky statements (might step on the gnomes' toes, since they have announcement capabilities, but something to consider), et cetera.
I found myself leaving a note for a new friend / neighbor that I was on a quest and I was fortunate that no one picked it up, so she could find me.