Steam's weekend deal should take care of any leftover PC gamers who've yet to experience the glory of The Orange Box, with the whole shebang available now for 66% off.
Unless you don't have $10 to spare, there is officially no reason why you shouldn't at least own The Orange Box by the end of the weekend. $9.99 gets you Half-Life 2, Half-Life 2 Episode 1, Half-Life 2 Episode 2, Half-Life 2: Lost Coast, Team Fortress 2, Portal, and some cake.
Okay, I lied about the cake.
The Orange Box for $9.99 [Steam]