Sid Meier's Gettysburg and Antietum are a couple of my favorites. They are real time, but more realistic movement and battle than the silly C&C model.

My absolute favorite is Steel Panthers. A group called SPCamo has reworked it and made it better over the years. It is available for free download, but is over 50 megs. So you need high bandwidth or a good download manager. This is turn-based, and plays just like the old Avalon Hills games like Advanced Squad leader. Without the charts of course :).

SPWW2

IT will run by itself, but you need one of the original SP cds to get video sequences between battles. Generally its better to buy SP2, then upgrade to SPWW2, to learn the game.

There is also another group that did a similar offshoot called SPWAW, (Steel Panther Worl at War), but I haven't tried it.

-Steve G.