Alongside the daily deals, Steam has cut prices on many publisher catalogs, not to mention the various greatly discounted bundles. For example, the 2K Mega Pack ($79.99) offers over three dozen games and expansions including BioShock 2, Mafia II, and Borderlands. Similar bundles are available for THQ, Bethesda, Square Enix / Eidos, Epic Games, Valve and many others.
If you happen to need a last minute gift for the casual gamer in your family, it's worth mentioning that more than 150 indie titles are also on sale in various $5 packs. As a reminder, today marks the conclusion of Steam's 'Treasure Hunt', so be sure to complete your objectives and log on before the end of the day for a chance to win 100 games of your choosing.