Fresh off the E3 presses (that show that no one cares about, right?): more Portal is on the way.
Information is scarce right now, but the sum total seems to be this: It’ll be released for the XBox Live Arcade, instead of as a boxed game. I think it’s assumed the game will also come out via Steam, but I don’t think there’s any super-official confirmation of that.
This second title, called "Portal: Still Alive" (Try Googling that to get some information. Is good time, yes?) will be a "continuation" of the original game, and include a "new challenge mode".
As Kotaku astutely notes, we were told in April 2008 that we "won’t see a new Portal this year". Since this new game is slated for release in 2008, it seems there have been some crossed signals.