Downloadable and very printable, I find these PDFs extremely useful.
Equilateral Triangle 
Octagonal 
Hexagonal 
Hex Dot
1/2" between closest dots. Black 
IsoDotsLike grid dots, but every other row is offset by half. These are not equalteral triangles.  
Tumbling Block  Trapezoid

Diamond  TrapezoidDiamond  Trapezoid PDF Generator

Equilateral Triangle DotsEquilateral Triangle PDF Generator

Semibisected TrapezoidSemiBisected Trapezoid PDF Generator Every other trapezoid is bisected into triangles. This is used for sketching piping and wiring diagrams for factory machinery. If you want this in landscape format, simply set your page size to wider than it is tall (e.g. 11x8.5). 
Variable Triangle 
This document is part of Incompetech.com.
©19982014 Kevin MacLeod