Downloadable Grids

This website is kind of a fun way to say how many columns etc you want in your grid. You can even say what point size you want to use and it will generate it.  It also has examples of designs using the grid.
http://sixrevisions.com/web_design/a-brief-look-at-grid-based-layouts-in-web-design/

http://www.thegridsystem.org/2009/templates/indesign-a4-gerstners-complex-grid-system-12/

http://960.gs/

http://www.teehanlax.com/downloads/baseline-grid/

good for a mobile grid too
http://cssgrid.net/

This has a few different options
http://crsindesigntemplates.com/free-indesign-grid-templates/blank-indesign-grid-system-templates/

This was just some research we did in class looking at grids. We went out and found grids we could download just so we can see how many columns are really used in a grid. I found that typically there is a whole but used in a grid even when it only looks like 3 or 4. It seems like its typically a high number grid and uses a 3 column layout which often fools your eye.