I was playing around with BigDB this weekend and i'm loving it. It's was hard to understand it's concept at first, since i have been using relational databases and SQL for years, but i think i'm getting the hang of it.
I put up a small demo on facebook, you can see it here:
http://apps.facebook.com/testmeoncenow/
If you get stuck at the "NetworkCommand" message for more than 10 seconds refresh the page. It's caused by the "code ran for too long" bug.
In this demo you can't see or talk to other players, but you can move the furniture around (just drag it), and it's position will be saved in the DB. Your character position will be saved too.
This demo was put together in less than 24h.
I used:
Flash Builder 4 (Flex framework IDE) : http://www.adobe.com/products/flashbuilder/
As3IsoLib (responsible for displaying almost everything you see on the screen) : http://code.google.com/p/as3isolib/
CasaLib (for bulk loading external assets) : http://casalib.org/
Greensock Tweenmax (for character movement) : http://www.greensock.com/tweenmax/
And of course PlayerIO (if you don't know the url there's something very wrong with you)