For the FOFL, there is an html form for file submission. The back end php program checks against the forum db for authentication, an ownership table for privileges, and then writes the file to an export directory. The script also writes who uploaded what file and when to a log (Radii actually helped out with this, iirc). IHOF uses a similar setup. We use ftp to retrieve the files for import.
Ideally, the game would store ftp credentials and directory location via a commissioner panel, and would have its own file export and import buttons/routines.