I just resubscribed to Planetside a few days ago actually, it's one of my favorite games... Cancelled my Xbox live subscription and replaced it with a planetside subscription again... I definately suggest you guys atleast try it out(it costs monthly though).
It's an online FPS type game(though you can switch to third person view by pressing -T-). Basically there are a bunch of different planets, on each of these different planets there is a continent.
Whichever empire you chose to start off with you try and conquer the continents which have already been conquered by other empires or are neutral bases...
There are a large variety of different certifications you can get that allow you to use different type of weaponry, ground vehicles, armors, planes etc.
There is a training zone where you can test almost all of the vehicles aswell as almost all of the weapons for your specific empire. Each empire has different weapons/vehicles that can be used, while some weapons and vehicles are usuable by all empires.
Anyways, that's my little shpeel, if anyone wants more information feel free to ask.
http://www.planetside.com
In fact, my signature image are my old stats from planetside along time ago, i'll need to update it soon.
My specific characters profile on the planetside site can be found here...
http://myplanetside.station.sony.com/character.jsp?charId=748340&worldId=15
WindowsXP Home(Service pack 2), Athlon XP 2400+(2.1Ghz), 1GIG Ram, Ati Radeon 9800Pro 128MB.