Apple Insider has posted that the pre-release of Snow Leopard OS X 10.6 will be on its way to developers shortly. This is the first release since the initial seeding during the annual developers conference in June of 2008.
Snow Leopard is not a major upgrade, but an upgrade to the core of OS X itself. The update is about optimization and core services rather than a feature set for the user. There is no known planned release for Snow Leopard, but one could only guess it will be ready in January for MacWorld.