Share is a Japanese p2p network. Most fansubbers get their raws from share, or one of its counterparts: The precursor
WinNY, or Share's successor
Perfect Dark. The files on there range from manga scans, to tv rips, to DVD images, to games, to pretty much anything you would find on bittorrent or limewire. The benefits of using these networks is that they are (almost completely) anonymous. However, subbers just like em because they are like a treasure trove of raws.