Mac OS X 10.5 "Leopard" will go on sale through Apple retail stores and resellers on October 26 at 6:00pm local time. Additionally, the company will accept pre-orders for the new OS beginning Tuesday.
Compared to previous releases, Leopard has taken a little longer for Apple to ship. Since the first consumer version of Mac OS X in March 2001, the company has more or less shipped a new version every year.
You may recall that the iPhone was one of the reasons this version took longer to ship. Developers were pulled off of Leopard earlier in the year to help complete iPhone development.