Okay, these are the last ones - parts six and seven of Valve's Portal 2 video onslaught which wraps up pretty much the entire Portal 2 presentation being given at E3 last month.
In these videos, Repulsion Gel turns any surface it's spread on into a trampoline, and Propulsion Gel makes you run like Sonic. Then check out the mental puzzles glimpsed at the end of Part 7 - it's going to blow your mind.
And see below for links to the rest of the videos.
Here are the rest of them: