Yes, there are some posts that try to summarize everything, but most of the are outdated.
What it all comes down to is this:
There are radios in portal, as there always used to be. You need to go get those radios, pick them up and carry them to some location. Suddenly it will start transmitting morse code or SSTV. SSTV is a way to transmit pictures through sound. In total, there are 26 radios, 4 transmitting morse code and the rest SSTV.
The best summary is here:
http://forums.steampowered.com/forums/s ... ?t=1169027
What this summary doesn't mention so far is, that they have found a phone number, used for BBS (a 90's forum system through modems). If you connect to it, you get some weird shit like this:
http://www.facepunch.com/showpost.php?p ... count=1441 (2nd picture is an elephant)
http://img341.imageshack.us/img341/6278/portalascii.png
http://i.imgur.com/Z01I6.png (blurred ASCII, so you can easily see the contours of the Portal sentry)
What it all comes down to is this: EPISODE 3 and PORTAL 2. Many of the hints feature some known theme (image, voice, ...) of one of the games. Speculation is, that the next part of those games will feature them more interconnected than before. (as we already know, Portal takes place in the HL universe)
The funniest thing is this: One radio transmit morse code, which if you spell it out translates to:
BEEP BEEEP BEEP BEEP
BEEEP BEEEP BEEEP
BEEP BEEEP BEEP BEEP
And if you translate that back it spells out LOL.
Valve is trolling us!