I've talked about Jeremy Ruston's excellent TiddlyWiki before. I've wanted to create a server based implementation for a long time but never managed to get around to it. Well, this weekend I did, and after putting it off for some time it turned out to be incredibly easy (thanks to jQuery).
It's based on the 2.4.3 version of TiddlyWiki (which is the latest version at time of writing), supports most plugins and themes, and in the future will support both xml/text and SQL Server backends. The SQL Server backend will also have optional (or maybe non-optional) encryption.
Requirements at the moment are pretty simple – IIS, and the .NET 2.0 Framework (although I'll be using LINQ for the SQL Server backend, so expect that framework version requirement to go up a bit).
Shortly I'll be looking for some testers and feature ideas, so if you've used TiddlyWiki before but needed a secure/online/web based version then drop me a line.