Demonoid is really easy considering there are no ratio requirements so there are so many leechers.
IPTorrents is also easy because of all those free leech torrents. Because of that I have about 50 GB Upload and nothing downloaded.
For ElbitZ all you have to do is add a torrent and then you'll get a bunch of people downloading it, and you'll be all set. Its as easy to seed as a site with no ratio requirement.
Overall though, I would have to say IPTorrents is by far the easiest to seed.
What is the easiest to seed for you?