The Book Practical Programming in Tcl and Tk, Fourth Edition contains an excellent introduction to the grid command, which is available online at [1].

Grid is excellent for many kinds of common GUI forms because it arranges widgets in nice rows and columns, and handles resizing quite nicely.

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A simple example is a panel with just a few labels and entries.

    package require Tk

    foreach field {Name Address City State Phone} {
        #  Create a couple of widgets
        set l [label .lab$field -text $field]
        set e [entry .ent$field -justify right ]
        #  Assign both to a row in the grid
        grid $l $e -padx 4 -pady 4
        #  Then adjust how they appear
        grid $l -sticky e
        grid $e -sticky ew
    }

    # X-resize is done by the entry column
    grid columnconfigure . 1 -weight 1

    #  Y-resize should be at the bottom...
    set lastrow [lindex [grid size .] 1]
    grid rowconfigure . [expr $lastrow - 1] -weight 1

For a little more complex example, see A little spreadsheet.

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On comp.lang.tcl, [2] describes how a change between Tk 8.4 and 8.5 causes code which depends on the grid default behavior may need to be modified. The specific example is the iwidgets disjointlistbox, but other code may find the same issue.

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DKF - The term Grid also refers to the very high end of resource sharing systems over the internet which it is likely that people will be hearing a lot more about in the future, especially in phrases like Grid Services...

TclGlobus is a project to allow Grid interfaces in Tcl: http://tclglobus.ligo.caltech.edu/