Richard Suchenwirth - This is my biggest and most favorite project since a long time: a geographic browser with map display and database browser. Most parts of it are on the Wiki at
Be aware that this is still in pre-alpha stage, but already running mighty nicely. Version 0.6 is at http://wiki.tcl.tk/_repo/wiki_images/tm06.zip
For maps in GIF images see iMap: an indexed map viewer
I first called this tkWorld, but then found out that this name has been taken by another software years ago, so now it's Tclworld.
A user (MPJ) has reported that he got Tclworld to run under WinCE on a pocket PC (check out the pictures on the Windows/CE wiki page). (RS) Another wrote "It works well on MacOS X, both on X-11 tclkit and Aqua Tk". More reports, also of problems, are welcome! Yet another adds MacOS 9 with Tclkit.
Rich map data are available e.g. from "Digital Chart of the World", http://www.maproom.psu.edu/dcw/ - downloaded text files (country outlines) from there can be loaded into Tclworld with the geo::dmc proc. Download US gazetteer files (plane names, pop., lat & lon) from http://ftp.census.gov/geo/www/gazetteer/places.html
onMouseOver="dcc('City or Large Town<br>Zurich, Switzerland<br>Lat: 47°31.42N<br>Lon: 8°52.54E','Adliswil'); return true;"
Save the page source and let regexp show its power to extract the various information, and reformat them for Tclworld, from lines like this ;-) At other times you might run into lists of thousands of airports or satellite stations - some editing may be required, but it's incomparably easier than measuring coordinates with a ruler on a physical map...