The Plot: You, a new test subject, Chell, are the new victim of the Enrichment Center, who is about to undergo the Portal technology testing. Not much of a story line, other then the fact that GLaDOS is now sane and the facility seems to be completely empty. Once you reach the end of the testing, GLaDOS tries to kill you in a fiery death, but she fails, hopefully because if you have died each and every time you glide into the fire pit you should probably close this document, not download Portal Taste The Cake and go take a long walk across a wide highway. Anyway, you eventually reach GLaDOS's chamber, which should look familiar, and GLaDOS starts to talk. Seconds later the Morality core falls out and for some strange reason, Chell throws it into an incinerator (why is there one in her chamber if all GLaDOS does is manage the facility, it's not like she has hands to throw away materials with) which sends her down in a spiral. GLaDOS now has an urge to kill her. After a few minutes of taking the other cores and burning them and redirecting rockets, eventually, GLaDOS's chamber is sucked out through the roof (why that would happen I don't know). This seems to be the end of Portal.
The Plot: This mod fills in the blank about what happened to the Borealis and what other chambers were on the other side of the walls. Eventually you escape and learn that you are a clone of many Chell's whether you are the first or the hundredth, the story doesn't say, but something must have been wrong with you to go against the computer's commands. Somewhere out in the world, the Borealis must have been shipping out cores for a Super Mech made by Aperture Science since not only do you load a container ship with them, but you also face one at the end of the game. GLaDOS must think you are too much for her, and actually lets you out through the garage door in which you fought the Super Mech. Once you get out, a ship can be seen in the distance. This is where this game ends.
The whole story is set up with Portal: Prelude, which as written above, sets up the entire story. Aperture Science is testing Portal technology, GLaDOS is turned on, and everything goes up in insanity. Now, at the end of Portal: Prelude, Abby seems to disappear, and unfortunately, isn't heard from again. Abby did play one major role though, she set Chell up. Once Chell entered the room, GLaDOS had to think about different results that could happen, so her cores were working in overdrive. Unfortunately, since Abby wasn't a mechanic the core was never properly installed, it was just placed in the right place where it was designed to go, so, without any welding or screws, it fell out. Once Chell set it ablaze, GLaDOS went insane just as she did when the core wasn't installed. The core stopped her from flooding the Enrichment Center with the neurotoxin, so, without it, she could continue flooding. Now, 3 cores later, Chell destroyed GLaDOS. Or so the story went. Look closely at the end credits, it says "Thank you for participating in this Enrichment Center activity!!" The entire game was one test, including the end fight sequence; it was all a single chamber. Using this, you were yet again, brought to the beginning of a new test, A.K.A. Portal: Flash Version Map Pack. At the end, read above, you were taken away in an airship and taken away. Just one little problem though, how is it that you go from exiting a garage to entering the facility in ruins? It's not like you were taken hostage for hundreds of years and just dropped off, there had to of been story between these events. This is exactly what we are here for. Without further ado, Portal: Taste The Cake.
The Plot: Portal: Taste The Cake, fills in the gaps that Valve never told you. Did you really think GLaDOS was that stupid to let herself be be accessed by a single employee that didn't belong, let alone a test subject that we think might as well be a clone. Everything that you thought you knew, was a lie, we are here to tell the truth. Portal: TTC introduces new characters, techniques, and technology, such as the Portal Paradox and the Matter Accelerator. This mod will shed light on why GLaDOS turns insane, how chambers are built, and the biggest secret of all, who is really watching if GLaDOS doesn't exist?
tl;dr.
(where are the pictures and videos to satiate the retarded masses?)
This is just the key to the storyline and how each thing flows together, this is more of a "If you want to read it you can" kind of article, not much else. This is just kind of a guideline, because this isn't explained in the actual mod.
Some things are, but certain things are a given.