Sully's is a large (about twice the size of Kimball Farm but with the same number of serving windows), solar powered, counter-service ice cream shop, located near Chelmsford High School and the associated sports fields (even though it's right off route 3, it doesn't seem like someplace you'd accidentally pass if you were from out of town.) Plenty of parking (but also fairly busy on a Sunday afternoon), and has a bunch of picnic tables (though some of them are on a hillside and might be difficult to get to.)
First Visit
They have a long list of ice cream and frozen yogurt flavors; I got Coffee Brandy Ice Cream which had a touch of sharpness to it, and paired that with Chocolate Walnut Ice Cream (basic, but a good change of pace from my usual Maple Walnut.) Next time perhaps I should find out if "Moose Tracks" and "Maine Black Bear" will fight with each other. Even with interesting and crunchy flavors (they did have Grapenut) they also have a chalkboard of specials that's worth a look.