At a hearing in Ohio, the House Judiciary Committee was told by a software engineer that one of its members asked him for software to rig election results four years ago: http://adam-t.dailykos.com/story/2004/12/13/18416/541

It has also been alleged that an employee of Triad, a manufacturer of optiscan voting equipment, attempted to tamper with an Ohio recount: http://www.bluelemur.com/index.php?p=490

Keith Olbermann from MSM writes about it here: http://www.msnbc.msn.com/id/6210240/
and cites a New York Times article.