You want to put them up as mpeg-1 (mpg) files which iMovie does not do. Export them from iMovie as full resolution which will give you a huge many gig movie that will be either a .dv or .mov depending on what version of iMovie you have and if it is HD or not.
Then use this to make you .mpg. It also does the copyright image on the movie.
http://www.popwire.com/product_info.php?products_id=2
There is a 30 demo of it.