According to Mac Rumors, the latest version of Leopard, 9A343 was seeded to developers on Thursday night. The last version seeded was on Dec. 13, 2006.
Apple actually has itemized a few of changes to Leopard from the last seed, including:
– HIToolbox provides new HIRect/Point/Shape-based Window Manager API for resolution independence compatibility
– Tab support in Terminal
– Terminal now lets you save a multi-window configurations through workspaces which are available through the “Terminal” menu.
– QuickLook APIs have been updated
Apple still lists Leopard as coming “Spring 2007″