This one's pretty good: http://www.texaspoison.com/snakes.asp
but since Howard is nationwide these days, it's tougher to have a list of enough url's to cover the whole country. Besides, folks always look at the wrong thing first. The color is the least indicative and most variable indicator of species, yet it's always what people start every description with. Pattern is also easily blurred when the snake is soon to shed (which happens more often than most people realize) so it can be dicey as an identifier also. I've had people send me pics of snakes that they had identified by looking around online, and marveled at how far off they were.