I wiped up a gear generator based on the MCAD 'involute_gears.scad' libarary
Hopefully, this makes creating gears very easy since all you have to do is plug in some numbers and press F6.

Options include:

• recessed sides (single or double sided)
• gear hub (single or double sided)
• set screw in the gear hub
• relief holes

UPDATE: V0.76
Added options for double set screws and setting the distance for the set screw from the end of the hub.
Renamed everything.
Added a couple of new examples.

Long video of a set of gears baking: https://www.youtube.com/watch?v=xEBrBUzchbU

Another video of gears in action:
https://www.youtube.com/watch?v=xbkGZLXumhg

Example to make a gear with recess sides, double-hubbed with set screw and relief holes (see attached image):

EasyBakeGear (circular_pitch = 88,   
number_of_teeth = 64,  
gear_thickness = 7,  
bore_diameter = 3,  
recess_thickness = 2,  
recess_diameter = 28,  
recess_double_side = true,  //default false  

hub_height = 12,  
hub_diameter=5,  
double_hub = true, //default false  

hub_set_screw_diameter=1.9,  
hub_set_screw_distance = 3,  // If 0 or missing, hole is centered  
hub_set_screw_double_sided = true,  
  
num_relief_circles=5,  
relief_circles_diameter=5  
);