Here's my suggestions,
Besides WinRar there's a file called Hjsplit. Like WinRar this allows you to break a file down into many parts, for a file 80 megs you can break it into say 5 megs and then instead of file.mpg you'll have file.001, file.002 etc. Users can then download each part then use Hjsplit to merge them back into one file - file.mpg.
As far as uploading have you thought about newsgroups?? Most isps, dsl especially have their own provider, you can post the files and when people download it they'll be downloading at the speed of their provider's download.
Bit-torrent is another good suggestion.