Here are three great turn based games, backed up by pretty nice communities, so you can fill that free time ;).
Wesnoth
The Battle for Wesnoth is a turn-based strategy game with a fantasy theme. There are 6 playable and balanced factions with several campaigns.
You can get additional campaigns, factions, maps by using the in game add-ons system.
Website | More Screenshots
FreeCiv
Freeciv is a Free and Open Source empire-building strategy game inspired by the history of human civilization. The game commences in prehistory and your mission is to lead your tribe from the stone age to the space age...
If you ever played Civilization I or II you will feel right at home.
Website | More Screenshots
FreeCol
The FreeCol team aims to create an Open Source version of Colonization
Website | More Screenshots
You can find these games in your Linux distribution package manager.
