…is in release 1.0 (blogpost) and available here. Haven’t checked it out yet, but I will – collaborative spreadsheet authoring would seem a great tool for research use, and perhaps also for making data available for public analysis.
Applied Abstractions
Espen Andersen's take on technology, strategy, and many other things
Applied Abstractions 
Some free test drives of wikiCalc in a server
environment are available on http://www.iwoorx.com which is in pre-release beta. But the test drives
are working.