Leftover flooring...

Do yourself and any future occupants of your apartment a big favor, and keep two boxes. Just in case the floorplan ever changes, a wall ever comes out, a portion of your apartment gets flooded by an upstairs unit, etc.

Trying to match floors (or tiles for that matter) after the fact is hell.

Build It Green is a good nonprofit that takes used appliances, furniture, architectural elements and the like. They may be worth calling. You could also see if Demolition Depot is interested.

By the way, have you contacted the vendor to see if they're willing to take back the unopened boxes?

Keep several boxes in case you ever need to do any work or any of the wood becomes damaged beyond repair.