OK so when you say "put" movies on your iPad, I am going to guess you not only want to carry them but you also want to play them on the iPad and that is the tricky part. you can "put" all the movies you want using, iFile, Cyberduck (SSH), IphoneExplorer, PhoneDisk, iDisk, etc. now they Won't play on the Ipod.app or video.app (in case of the iPad) this application need no only the video file but also some entries on the database that cannot be done manually.
Now, I think there are some alternatives media player you can use to play those videos, i think iFile got a build in player you could use (very basic) and there were other media players out there I can't remember their names from the top of my head now and I am not sure if they have been updated lately to support iOS4