Although the Steam Summer Sale is right around the corner, Valve has decided to give their largest franchise a headstart. At 75% off you can get Half-Life 2 and its Episodes for a couple of dollars/euros/whatever currency you're dealin with.
But for $9.99/6.99€ you can get the complete Half-Life package, which includes Team Fortress Classic, Half-Life: Opposing Force, Half-Life, Half-Life: Blue Shift, Half-Life 2, Half-Life: Source, Half-Life 2: Deathmatch, Half-Life 2: Lost Coast, Half-Life 2: Episode One, Half-Life 2: Episode Two
If you already have some of these, the individual titles are also available at 75% off (except HL:Source and HL2:Lost Coast which are only available through the package.
Half-Life 2 is one of the first big games to recieve Rift support, so if you have a Rift or have one coming and you don't own HL you should jump on this offer which expires on Thursday. Hell, even without a Rift, this is a deal you can't pass up.