TripleA Maps
TripleA is a free turn based strategy game and board game engine. Has single player vs ai/hot-seat, multiplayer through Play By Email, network play, and a hosted Online lobby. Comes with 4 games, and over 100 more games and maps that can be downloaded. Needs only Java to run, so can run on Windows, Mac, Linux. Supports features like savegames, encrypted dice gen, low luck, and many more options.
If you need the latest version of the TripleA game engine, please visit https://sourceforge.net/projects/triplea/

TripleA comes with, by default, just 4 maps (Big World, Great War, Capture the Flag, and Minimap), so you must download more. Here is how:

All you have to do is start up TripleA 1.2.X.X (Yes that means run the .exe or .sh) and click on the "Download Maps" button.
A dialog box will open where you can add links to "Map Repositories" (sites that host maps).
Here's is the best one to add:
http://downloads.sourceforge.net/project/tripleamaps/triplea_maps.xml

AGAIN, Just take the link (the long http one that ends in .xml), and copy it. Then open up TripleA, click on Download maps, then PASTE it into the blank box there, then click "list games". (clicking the links to the .xml, or opening them in your web-browser, will do nothing for you). Here is a Slideshow showing how to do it.

If you wish to download the maps Manually, please download them to your computer from https://sourceforge.net/projects/tripleamaps/files/

For further help, or to ask a question, please visit the FAQ page on our ForumA project by Veqryn for creating, centralizing, and hosting all open-source TripleA maps, as well as other developer resources such as artwork and map makers.
Pictures of the Maps available from http://downloads.sourceforge.net/project/tripleamaps/triplea_maps.xml