In addition to the NAFTA in 1994 obviously, they have signed with Australia in 2005, Chile in 2004, the Central American Dominican Republic in 2005, and Singapore in 2004. They signed one with Oman in 2006, yet it's not yet enforced. They signed with Morocco in 2004. So there is a good cross-section across the world.
On October 17th, 2006. See this statement in context.