If you’re looking to share files privately with friends using BitTorrent, have a look at this link on TorrentFreak which gives a description on how to do this using various popular BitTorrent applications. To make the Torrents public to anyone, just use the “Upload” facility on your preferred BitTorrent tracker websites to make them public.
Just be sure that the content you plan sharing is public domain and does not have restrictions on copying or distribution! If you are not sure (e.g. music, video, etc. files someone gave you, which does not have any copyright info, etc.), then it’s best avoid sharing it to be on the safe side.
Note that once you create a Torrent, no uploading takes place until someone tries downloading what you have shared out. Unlike dedicated file uploading websites (such as Rapid Share, etc.), the files shared are only shared by end-users and not a central server.