I've seen Wiki's being used as a technological base for playing Universalis, but I'm not aware of any wildly successful runs with that.
Are there any other good web tools for universalis?
I'd recommend mind-mapping collaboration tools like MindMeister (free) and Mindomo. Also, some of the virtual tabletop tools might work. Just create some kind of index card system on the VTT and record information that way. VTTs also roll dice, in case you need that, too.
What about mutli-user editors?
One rather recent (and diabolical) example of this would be Google Wave or Docs. I actually thought about using one of these for a tabletop round of Universalis (with multiple laptops for the participants). That would have saved a lot of global looking-up of facts and handing around the computer to the next scribe.
Ning used to be a great resource for this kind of stuff. You could start a network. Any particular game could be a group within that network, and each scene could be a thread in that group. It also had chat, man, I was sad when it went to a pay only model, but there are probably other social network platforms out there. I just haven't looked into it yet because I haven't been able to put together the people interested in doing it.
I would love to put together another place on-line for diceless games, maybe get some Mortal Coil going on.
a nice wiki based tool is the obsidian portal but for collaborative editing of basic files we use dropbox (of which there are many similar programs).
From what I know of Universalis (almost nothing) wouldn't play by forum work well? There is a specific timeline for each players input (avoiding the two people attempting to influenec the story at the same tiem that you will get in chat or IM style) and you can have as many topics (scenes) as needed.