How do I exit extrude? When Blender starts, the default cube appears in object mode. If I tab into edit mode, and right click onto the cube, and then drag - it extrudes without my pressing E or clicking on the extrude button. Also, the extrude button is hi-lighted at all times. Is this a bug, or am I doing something wrong?
When you drag with RMB, you move the selection.

Press esc to leave the mode without changes.

If you want to select without moving, you've to release the button immediatly.
If you extruded (e), you'll add new vertices.