We're off topic. He wants to know how to make a flash portal.
Well, I think that it's purely php combined with html forms. Just find connections between the forms and the pages that have flash on them. When someone presses the submit button, all the information they give goes into php scripts. Not only does it create a page based on the information, but it also sends the flash file to "ungrounded.net" where all the flash on Newgrounds is stored.
Moreso, it edits the front page of the flash portal by adding a link to its location and removes the link when it's blammed. If you are to make a flash portal, you need to set up the correct algorithms, (voting, total vote, ect.) learn the corect php scripts, (I suggest reading up here till "file upload," unless you don't know any php, in which I suggest you read the entire thing.) and actually have a server that can support the massive amounts of files, people coming in and out, actions, functions, ect.
Yea, a flash portal doesn't seem any easier, does it.