Miyamoto Musashi. He is the famous swordman of the XVII century that created the Hyoho Niten Ichi Ryu school of swordmanship.
His most important writting is the Gorin No Sho (The Book of Five Rings, or more accurately translated as The Book of the Tombstone).
Anyone interested in using the two swords (daisho) should take a look at Musashi's school. Of course there is also the Tenshin Shoden Katori Shinto Ryu, certain branches of Daito Ryu and Saotome's Two Swords of Aikido for example.
Some techniques can be found in Anji-san web site (Kampai Budokai).