1. Companion cube and other Portal paper toys.
2. Aperture Science logo wallpapers (Wheatley, too).
4. An interesting interpretation of what happens at the end of the game.
5. There's a Portal 2 iPhone app that sounds incredible.
6. Destructoid's review of Portal 2:
Portal 2 is, without a doubt, one of the best games ever made. It's a game that not only seamlessly blends puzzle and adventure elements together, but makes a name for itself as a true "comedy" game, where witty dialog and laugh-out-loud concepts have been given an equal billing with the gameplay itself. It's funny, it's challenging, it's inventive, and it boasts memorable moments that will stick in your mind and make your hair stand on end every time you think about them.7. Seriously, even if you don't like playing games, you should watch the single and multiplayer campaigns.