First thing I recommend is getting the book "Great Sausage Recipes and Meat Curing" by Rytek Kutas. It has more recipes then you could hope to make in many years, as well as safety information and explanations of ingredients and cures. Quite literally a "bible" for sausage making.
I use a 50/50 mix of venison and pork butt for summer sausage and many other recipes. Breakfast sausage I use straight pork.
I particularly like the summer sausage, breakfast sausage, and sweet Italian recipes from the book. Modify seasoning to your own tastes.