Mojang is going nuts with the Minecraft updates, releasing 1.2.5 earlier this morning. New in this release is new behavior for TNT, specificly while using flint and steel. Left-clicking a TNT block with Flint and Steel will drop the block, and right-clicking will fire the TNT. Also new is shift-click support with furnaces, minor changes to cats, no more 'ghosts' in multiplayer, and various other bug fixes. Unfortuantly, the new release has many documented bugs, making it more like a snapshot than a release. To get the update, open Minecraft and login, then push Update when asked.