Two kinds of poplar
Around here, poplar might mean
Quaking Aspen (GENERAL: A medium sized tree, typically reaching 60' high, of rapid growth but short-lived. Most common on sandy or gravelly soils of old fields and open woods in northern Pennsylvania, but it can be found throughout the state. Important for revegetating recently cut or burned areas by sprouting from widespread roots. Its wood is used chiefly for pulp in manufacturing paper and cardboard. Many animals browse the twigs and it is a favorite food of beaver.
I agree with the "junk" opinion, I don't mess with it, too many other trees that are worth my labor.
On the other hand:
Tulip Poplar. (GENERAL: Also known as Yellow poplar, Tulip poplar, White poplar and Whitewood. A large tree, the tallest of the eastern hardwoods. It grows rapidly and is an important timber and shade tree. The wood is valuable for veneer and many other uses. Songbirds and game birds, rabbits, squirrels and mice feed on the seeds. Whitetail deer browse the young growth.)
Here are the links with leaf pictures:
http://www.dcnr.state.pa.us/forestry/commontr/tuliptre.htm
http://www.dcnr.state.pa.us/FORESTRY/commontr/quaking.htm