This is a customisable stencil built in OpenSCAD. You can choose a font from a massive library and the size of the text and print the entire alphabet or an individual letter. Great for spray painting, art work, etc.

As user codifies noted, letters A B D O P Q R will not be connected. I uploaded an example where I modified it by manipulating a simple rectangle cube in repetier host and exported it as one stl. Of course other cad programs might make it easier. You can get an example of how to join your characters on google.

EDIT(18/02/17): Added Options for 1,2 and 3 lines.
EDIT(19/03/17): Removed width and height as its caculated from font size