I've uploaded on GitHub a script that allows you to extrude selected vertices in all directions.
You can set the amount and choose whether select created vertices or not.
How to install
extrudeVerticesAllDirections.py in the Text Editor and press Alt+P
How to use
- Select a mesh object and toggle into Edit Mode (Tab)
- In the MISC tab of the Tool Shelf (T) you'll find a new Extrude in all directions panel
- Set the extrusion amount and whether select new vertices or not (if not, original vertices will still selected)