The Seven Swords include:
Kusanagi-found by Susanoo when he encountered a grieving family who told him they were being tormented by an Opochi, an 8 headed snake monster. When he killed it, he found Kusanagi in it's throat. It gives it's owner the power to control wind. The second most powerful weapon in the world next to....
Amenonuhoko-Used by Izanagi and Izanami to create the islands of Japan by churning the water. It basically created the world, since in mythology all other landmasses grew from former Japanese islands.
Tonbogiri-created by Masamune's rival Muramasa, and when a fly landed on it's blade it was instantly cut in two. The Sword of Destruction.
Tokugawa-This sword was made by Masamune to defeat Muramasa. It is linked to death and was destined to defeat Muramasa. However, the sword was clouded by Masamune's lose of judgement, saw it's creator in the mirror (who looks just like Muramasa if you flipflop him) and killed him instead.
Masatada-a failed attempt at Masamune and Muramasa made to settle their differences. They tried to make a sword of friendship that could kill any foe, but when it was stolen and used to kill a shogun, they started blaming each other and went back to fighting.
Mumei Wakazashi- A sword that would never need restoration and would always remain beautiful and fresh. However, it's made out of pure gold, so it's completely useless as a sword.
and of course...
Masamune-The sword that started it all. This is the sword that caused the bitter rivalry between Masamune and Muramasa. The Emperor was amazed and delighted after seeing that Masamune's sword was able to magically repel leaves and similar small objects. It had an aura of peace and serenity, and anyone who tried to use it for evil died a horrible death by the very sword they wanted to corrupt.