i've been looking at inventory and myplaza mod, and it seems like they are no longer being developed. (not sure inventory, but the website no longer works, so i'm just assuming)
Is there one that is still actively being worked on?
MyPlaza is still being developed from what I know.
http://myplaza.zingaburga.com/ is the site but it seems to be having problems right now. Hopfeully Zinga will be able to comment on this.
I might get rid of that MediaWiki script - have no idea what happened to it.
MyPlaza is quite low on my priority list actually, although the only thing that really needs upgrading is the AdminCP (write a few extra wrappers).
I'll say that I've somewhat halted development on it. I might update it for 1.4 in the future, but not terribly soon.