TiddlySpace is another tiddler hosting service. It was created by the Osmosoft group at BT. In late 2013 BT laid off or otherwise encouraged the departure of the people responsible for maintaining it. For the next two years it continued to run, essentially unmaintained, as a useful service. In the end of 2016 it was scheduled to be shut down.
You can read about the differences between TiddlySpace and Tank.