After logging on to ApertureScience.com, type ? or LIB to see the following list of commands.
Type DIR then type APPLY to take an application for entry into the "Enrichment Center".
While logged into the ApertureScience.com site, type THECAKEISALIE to access an interesting message left by some employees.
The graffiti in the game are clues for the web site. Go to the site and enter LOGIN as a command. Enter CJOHNSON as a username and TIER3 as a password. After logging in, type HELP for a list of commands.
In addition to logging in as "CJOHNSON" (Chell), you can login as anyone desired by typing a username longer than two characters and using PORTAL as a password.
On the level where you get the companion cube after you run past the energy balls and are in the room with the three elevators, there are two doors leading to a catcher, and a platform that is pushed out of the wall. Walk up to the platform that is pushed out. Crouch behind it and walk through the opening. On the left hand side are a group of pictures of people with boxes for heads and hearts around them.