The Orange Box is a five-in-one package of games by Valve Software, the creators of Half-Life. The Orange Box contains:
The Orange Box costs $49.95 on Steam (Valve's games download system), which makes it excellent value even if you already own Half-Life 2 and Episode One, whereas buying Episode Two and Team Fortress 2 separately would cost you $59.90. Plus, if you purchase The Orange Box and you already own some of the games in it, you'll receive Gift codes for those games, which allow you to give someone else a copy of those games for free.
NOTE: My PC is over four-and-a-half years old now (Pentium 4 2.4GHz, 512MB RAM, Radeon 9700 Pro graphics card). I can still play the games, but only in the low graphics settings. So bear in mind that the screenshots will not be representative of what the games are fully capable of.
UPDATE: In June 2009, Valve added support to The Orange Box games for the Novint Falcon PC game controller.
If you're a fan of first-person shooters and you haven't played Half-Life 2 yet, you would be mad not to get yourself a copy of it. (If you're not ready to commit to buying The Orange Box yet, see if you can persuade someone to give you their spare Gift copy of Half-Life 2 once they've bought The Orange Box themselves.)
After the Black Mesa incident in Half-Life (which you should also have played by now), Half-Life 2 drops you into a world ruined by alien parasites and powerful armies using other-worldly technology. You reprise the role of Gordon Freeman, former Black Mesa scientist, thrown back into the mix by people with unspecified agendas. You then set about tearing down part of the new world order that you unwittingly helped to install.
Half-Life 2 is an incredible game, mixing first-person shooter action with incredible character animation and dialogue. You race across canals and roads in vehicles, fight aircraft and alien fighters that tower above you, and get to learn just a little more about what drove the events at Black Mesa.
Half-Life 2: Episode One carries on where Half-Life 2 ended. It's very much based in the corridors and basements of City 17, and lacks the feeling of freedom that the early chapters of Half-Life 2 offer. It also lacks story development. Nevertheless, it's another solid chunk of action.