This table from Iowa website gives a nice chart showing the various herbicide families.

This chart from Purdue does the same thing in a slightly different format.

This page from NCSU gives a lot more reading info on the various herbicides, although I don't know if this page contains all the families.

Here's a nice introductory level publication on weeds and herbicides.  It has some of the tables listed above.  However, at the end of the publication, it has herbicides listed by relative toxicity, and also some other products as well.  Interesting to read thru this list.....