A "running spider," or "sac spider," in the family Clubionidae. The genus is Trachelas, and the species may be T. tranquillus. They frequently enter houses by accident in the autumn, looking for hibernation spots, or possibly mates. They are harmless, but pale (light grey or beige) clubionids in the genus Chiricanthium have been implicated in mild human envenomations, so watch out for them.

(Identification and description courtesy of Eric Eaton. bugeric@webtv.net)