Vengi on 05 November 2007
the only game I've heard of that is like portal is Narbacular Drop which was what inspired/turned into Portal.
The GLaDOS is the star of Portal for me, really really funny, I have the mp3 of that song. 
I tried hard to trap myself but the game always gives you a way out :P
There is a commentary mode in the game - one part explains how they had to rework all the physics within the portals "bubble of influence" so that the game didn't slow down.
"..just keep on trying 'till you run out of cake"
