TiddlyWiki can also be hosted on online services such as Dropbox and Cloudant.

Dropbox (syncs the entire HTML file)

To edit files stored in your Dropbox, go to http://tiny.cc/tw5inthesky/. This will allow you to open any HTML files found.

Cloudant (or another CouchDB-type server) (syncs individual tiddlers)

http://noteself.github.io/