As a writer, I use grids often; they help me keep ideas organized when I'm brainstorming and making outlines. When I found these two extensive grid resources, I knew I had to post them here. Based on what I know about this blog's readership, you all will enjoy and reference these sites:
1. The Grid System bills itself as the "ultimate resource in grid systems". Based on what I've read so far on the site, this assertion may be correct. From article and book links to tools and templates, this exhaustive source hosts a stunning amount of grid-related information.
2. Incompetech features 44 different grids and other lined paper, all available free as PDF downloads — everything from traditional graph paper to cross grids to iso-dots to music notation paper. The above image shows four additional kinds found at Incompetech.