Cowles Lake near Venice, Nebraska, is commonly known as "the trout lake" because it is seasonally stocked with rainbows, but it's also a good spot for black crappie, dragonflies, and amphibians.
American toads only occur in a couple of eastern counties within Nebraska, and this lake is the most reliable spot I know for them.
Plains leopard frogs occur here in decent numbers, and are easily recognised by their brown colouration. (Northern leopard frogs are patterned similarly, but in green.)
By far the most conspicuous, however, are bullfrogs.
[All photos by Jessica, with the exception of the first leopard frog by me, and this one by Ellie of Jess holding a developing bullfrog.]