What type of poplar? There is aspen and tulip poplar. My understanding is that alder is pretty much like tulip poplar.
Tulip poplar is used in anything from interior furniture parts to architectural moldings. We sell quite a bit to the casket companies. Tulip poplar will take a stain very well, and will look quite a bit like walnut or cherry. They also make paint grade cabinets from tulip poplar.
You should be able to find a market for that alder.