"tktoolkit" is the label used at SourceForge to identify Tk as a project. D. Richard Hipp also maintains a sort of mirror [L1 ] with SF snapshots, as a CVSTrac demonstration. (DRH - Nope. I made a snapshot of the CVS repository some time ago, as a demo, but it has long since been taken down.) The demonstration's "timeline" [L2 ] thus constitutes a convenient view on the history of core Tk check-ins (but will CL fulfill his threat to provide a CVS automation to achieve roughly the same?).
DKF: A more suitable timeline view is http://core.tcl.tk/tk/timeline though you should be aware that it has many things going on in it; it's an ant's eye view, not the view from 40000 feet!