Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
By Richard M. Baranowski. Written in 1986, this key is available in both JPEG and PDF format.

Here is a direct link to the key.
http://palmm.fcla.edu/feol/feolAuthorList.html

dead link :/
should be in Books, not Links: it's a printed paper [available online, too]
http://ufdc.ufl.edu/UF00000092/00001
NB: there is a Books entry already(1)