Apparently Steam/Valve have been busy. The Portal community has been blowing up the last few days... why?
In a nutshell:
Portal gets surprise update March 1st
People see new mystery achievement
People play and see the radio in the beginning room now has a green light
Carry it around and notice it makes strange broadcast interference noises in certain places
Locate and place all 26 of these mystery radios for achievement
Smart people yank stange wav files out of game content folders and run them through steganography programs
Produces 26 weird cryptic image files in a numbered sequence
Some dude runs the number string through an md5 hash translator and gets a landline number
Internet traces it to Kirkland, WA (near Valve HQ)
People find out its not a phone/fax line but a data line hosting a BBS and telnet to it
Use a clue from one of the files to figure out the BBS user/password login info
End up with a bunch of weird ASCII artwork which is related to Portal.
March 3rd Valve sent another mystery update to Portal
BBS login switched to a countdown
Countdown expired today when this single message was posted on Steam's site:
http://store.steampowered.com/news/3559/With cryptic underlined characters.
People decipher characters in to another login for the dial-up telnet system, and get some QBasic code.
People execute QBasic code and get 2 more images.
One of the WAV file's spectrogram... looks strangely familiar.

Here is 1 of the many many ASCII arts they have gotten

Someone rendered this based on the ASCII art

Here are the 2 images people retrieved from the QBasic code:


What does this all mean?
Well, Game Informer broke this:

Basically, this October we'll be getting a FULL Portal game. Big game, many levels, CO-OP play!
This is all incredibly nerdy, and I'm so excited to finally get a sequel to one of the funnest most original games to come out in more then 5 years!
I'm tempted to take my laptop to my Dad's land line tomorrow and dial up to the BBS just for the heck of it.
Oh yeah, there are quite a few ASCII art images as well... if you want to check out the rest:
http://portalwiki.net/index.php/Known_ImagesRead about the wav files:
http://portalwiki.net/index.php/Dinosaur_SoundsRead up on the whole puzzle if you like:
http://portalwiki.net/index.php/Portal_Puzzle_Overview