@CrimmyI've made pork, lamb, and margharitta mix sausages, but having never done poultry, I can't say if it exists. It usually comes down to issues of contamination.
Chicken - Can't give it anything worse then it already has.
Lamp, Pork, Goat - Worse then beef, but not so bad you'll start an e-coli outbreak if your careless.
Beef - Most easily contaminated of all.
So when it comes to sausage, you want to use the middle ground meat, Tzi :3