Undescribed sheetweb spider (Linyphantes sp.)
This is a tiny (a little over 2mm in body length) sheetweb spider in the genus Linyphantes. Like many sheetweb spiders, her species builds small, flat webs in leaf litter, under moss, and in other damp locations. As of yet, her species has not been formally described.
She, along with many of the other spiders in this gallery, was kindly identified by Rod Crawford, curator of arachnids at The Burke Museum.
More photos of her on BugGuide:
http://bugguide.net/node/view/724159