Here are links to some pages in the Tcl'ers Wiki which give Tcl/Tk code examples. See also Tk syntax help - Widgets in the initial Tk package - Tcl examples - and just look around; e.g. RS is too lazy to bring all examples to this page too. -RS: Maybe lazy, but there's so many of them... All my fun projects, Tk or not, are listed on the RS page.
Button widget
Text widget
Canvas widget
Others