Info
This tool will grow polygon selection based on "Edge Angle", i.e. angle between normals of 2 polygons sharing particular edge.
In other words. You've got selected polygon(s). Adjacent polygons will be added to selection (selection will be grown) if Edge Angle between polygons is in some range (set in UI). This growing will proceed until there is no valid polygons to grow.
Similar tool called "Select by angle" can be found in 3DSMAX.

Features:
- Handy interface
- Fully interactive. Tweak controls and immediately see results in viewports.
- Implementation of 3DSMAX "Select by angle"

Installation:
Put this script in your PYTHONPATH directory.
In Maya, run this script by typing in "Python" tab of Script Editor or make a shelf button containing:

import fx_growSelectionByEdgeAngle
fx_growSelectionByEdgeAngle.run()