ValVe have confused things a little with the release of The Orange Box as there is no one place where you can get all the information on what you are getting in the box, so let me try and straighten things out.
The Orange Box comes with Half Life 2, HL2 Episode One, HL2 Episode Two, Portal and Team Fortress 2. It will be released for the PC and XBox360 on October the 10th with the PS3 version (which is being ported by EA) released at a later date.
If you Pre-Order over STEAM then you will get a 10% ($5) discount on the price. Access to the Team Fortress 2 Beta which starts on the 17th (this Monday). And a copy of Peggle Extreme which is a short ten level version of Peggle that comes Half Life 2 themed.
If you already own Half-Life 2 and/or HL2 Episode One then ValVe is suggesting that you Gift them to a friend when you buy The Orange Box over STEAM. This seems silly, but I think they did that to prevent confusion with multiple versions of the Orange Box as there was originally going to be a Black Box at one point without HL2 and HL2-E1, but that idea was scrapped a few months ago in favour of the single release.