Toolbar is a pretty common term.  So the reader should not be surprised
if they find various ways of creating such a thing.

[CL] adds that it's not just a common term; it's also the kind of construction
[Tk] (among other toolkits) makes easy, so it's been implemented over and over
(and over.  and over).  As [Victor Wagner] once posted, "just ... [pack] 
(or [grid]) some [button]s into [frame], [bind] <Enter> and <Leave> items 
to change images.  I doubt that making this a package would be simpler, 
than hacking it on the spot with core Tk commands."

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For instance, [Iwidgets] has a toolbar command:

[http://incrtcl.sourceforge.net/iwidgets/iwidgets/toolbar.gif]

Docs can be found at http://incrtcl.sourceforge.net/iwidgets/iwidgets/toolbar.html and http://purl.org/tcl/home/man/iwidgets3.0/toolbar.n.html
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http://www.iit.demokritos.gr/~petasis/Tcl/toolbar.tcl provides dockable toolbars.
See also [ClassyTk] (and [mkImagesPane] for code that could be used to create
a toolbar).

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[Bwidget] has a MainFrame widget, which includes a toolbar created as a ButtonBox 
(a series of Bwidget buttons).

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[MG] is playing around with a [Customizable Toolbar Widget] on Dec 21 2005.

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[xf] implements a toolbar.

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[Category Command], a part of [incr Widgets] - [Category GUI]