Yesterday
Valve released the new updated tools for the Source engine allowing you to tweak Portal 2 until your hearts content. Grab them by downloading the authoring tools beta in the tools section of Steam.
Also in other news, an in-depth interview of one of the writers for Portal 2: Erik Wolpaw talks about the game and the state of game stories in the business. It's pretty lengthy at about an hour twenty, and full of interesting insights.
Give it a watch!
Also as a follow-up to the Mike Morasky interview from a week ago; the live interview fell short due to technical difficulties and was postponed. The interview carried on behind closed doors and is now available to the public. -Really interesting stuff!
Check it out!