• http://www.wesnoth.org/
• http://www.linuxlinks.com/article/20080510052539217/Games.html List of Linux Games Part I
• http://www.linuxlinks.com/article/20080522164112313/Games-Part2.html List of Linux Games Part II

I really enjoyed Panzer General, and recently found this page where you can download a LOT of the classic SSI games.