I bought Triangulations 2.0 and LOVE it. Simply measure the size of square you want to end up with, find the matching page and print it out. You get a page full of triangles that are sewed all at once, then trimmed, opened and pressed before removing the paper. Is this cheating? I don't know, but no longer worry about triangles!
http://www.bearpawproductions.com/triangulations.htm