I'm interested in planting 2-3 trees on the west side of my house and I was looking for ideas on what kind of shade trees to plant.

I have several acres, so a large size shade tree is no problem. It also doesn't have to be the fastest growing tree in the world. My main priority is something that give a decent shade, and doesn't stay puny.

I live at about 4100 feet between zones 7 and 8, so I do need something that will take the frosts and occasional snow.

Any ideas?