So its fairly well known of a game, probably one of the coolest I've personally come to love (not enough companion cube though) but anyhow, i stumbled on the coolest thing for portal, cool enough I wanted to share.
I stumbled on this video and played around with the editor [link]
It is so goddamn simple it almost makes me want to cry. I'm still playing around with it myself, but hell, i think anyone can make something awesome with this.
edit: I apologize if this is old news to some folks, I've been looking for something like this since orange box first came out.