Panzer General Online is looking pretty slick for a browser-based thing, which I suppose shouldn't be surprising: the tactics game is being rolled out by Ubi as part of their new free to play offensive. And it's not relying on multiplayer, either, as they explain: "In the singleplayer campaigns you lead your army through historically inspired missions. All campaigns can be played as either the German or the US army." Quite how much territory this will capture them isn't clear to me, but it does seem like it could be a big deal in WW2-fancying tank circles, if just from the lovely presentation.
Anyway, the closed beta can be signed up to over here. So you should probably get on that.