Planet Half-Life has a story about Half-Life 2: Aftermath, the Lost Coast HDR level and Half-Life 2 Xbox. From Valve's Doug Lombardi

Half-Life 2: Aftermath is due in late summer. The episode continues the adventures of Gordon Freeman, and begins immediately following the conclusion of HL2. It will be available via Steam and may appear in retail boxes as well. It is not slated to appear at E3. Lost Coast is slated to appear in the Games for Windows areas at E3, and is scheduled for release during the summer months. Half-Life 2 Xbox, featured on this month's issue of the Official Xbox Magazine, is slated for completion in August and will be shown in Microsoft's booth at E3.