IGN.PC has a bunch of screenshots of Half-Life 2: Episode One (formerly called Aftermath). Episode One is an episodic content for Half-Life 2, and will likely last around 6 hours of gameplay time. Not that much, but Episode Two is rumored to follow hot on the heels of One. Here’s more information about Episode One:

Half-Life 2: Episode One is the first of a series of stand-alone episodes based on HL2, the popular and acclaimed shooter epic. This episode takes place right after the events in HL2, and you and Alyx will flee from City 17, fighting against creatures who were previous blocked from enetering the city. The Citadel you assaulted in HL2 is tumbling into chaos, and this event will have catastrophic effects on the surrounding area, prompting your escape. Secondary characters Alyx and Dog will have a much more significant role in this follow-up.