GameSpyDaily has a report up quoting Valve's Doug Lombardi as he confirms Half-Life 2 production for the Xbox gaming console:

Lombardi today told GameSpy Half-Life 2 is certainly in development for the Xbox. "Half-Life 2 is planned for the PC and Xbox. We've announced the shipping date for the PC version [September 30, 2003 - ed.], and we'll announce a shipping date for the Xbox version later in the year.