Add vertex snapping capabilities for curves. Snap to unhidden control points of other objects, and unhidden, unselected control points and handles in curve edit mode.
Note: unclear if it should snap to hidden control points on other curves or not. Just needs decision, having ability to hide stuff to not obscure snapping in object mode is good, but hidden/unhidden is not visible outside curve edit mode, so might be confusing.
Todo from http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools

Also came over as http://developer.blender.org/T37358 from the old patch tracker.