Chris linked to this:
I spent 10 minutes after watching this (in broad daylight!) freaking out that one of my flatmates was sneaking up behind me with a big smile on their face.
To mellow out, I re-played You Have to Burn the Rope. Seriously, you should. And stick around for the end credits song. Portal's is better, but this is fun.
And if you liked YHtBtR, you could check out Fathom. Pay close attention to the fish.
I thoroughly recommend the Google Wave presentation by the way. Yes, it's 80 minutes long, but I especially the last 5 minutes, where the development team demo the app that's going to bring about world peace.
Here's a link to the highlights reel.