This game's pretty good..
It's a self proclaimed "Massively Multi Player Online Tactics Game".
You buy and upgrade ships, recruit and level sailors, trade stuff and fight sea battles with up to 128 players. It's sorta like a WW2 version of Pirates and Scorched Earth. The battles are fun, especially when there's a large amount of ships and planes blasting the hell out of each other in real time.
Some screenshots:
http://navyfield.com/us_1/screen.asp?gc=1&mc=1
and the download:
http://navyfield.com/chkcount/chk_downl ... ton_manual