I pick Hello Fall for my favorite fall collection. Love the blue thrown in with the other traditional fall colors.
Carta Bella's Autumn line is my second pick...love the bright colors.
3rd would have to be Echo Park's "Fall is in the Air"...the colors with a hint of teal, perfection!
Photo Play has their own fall line called Falling Leaves.
Reminisce has their Best of Harvest collection.
These next two aren't specifically fall but would work for both fall and outdoor photos. The fox in Jillibean Soup's Mushroom Medley line (2nd photo below) is just too cute. If you're at a crop in November, I will be offering a two-page layout class using this line.
Plenty of Fall lines to choose from...last but not least, Authentique's Harvest