Howdy! Because of vandalism, the old NotebookWiki has been taken off line. You can follow Notebook development at the Notebook Bug Tracker.
NOTE: The Bug Tracker is back up again!
You can download the current development version, Notebook v3.0.0, from the Notebook bug tracker (see above).
The current stable version, Notebook v2.1.3, can be downloaded here:
V2.1.3 is available as a Windows executable, a Native App for Mac OS X, as a Starkit, and as Tcl source code.