Valve's Orange Box was already a great deal in itself but it's even more so this weekend. The bundle, which includes Team Fortress 2, Portal, Half Life 2, Half Life 2: Episode One, Half Life 2: Episode Two and Half Life 2: Lost Coast (a tech demo level), is 66% off its regular price on Steam starting today and until Sunday - that's $9.99 for the whole pack which includes the actively updated TF2.
There's really no reason to miss out on the deal, whether it's the great multiplayer fun of Team Fortress 2 or the engaging story and gameplay in Portal and the Half-Life 2 series. Also, if you already own any of the titles included in the bundle, you can give it to a friend as a gift. More info is available here.