Some of these are older versions, but should work perfectly fine in most cases and cost a fraction as much as the latest edition. :)

Econ 118 - Development Economics (Ray 1998)
Like new. $40.

Econ 52 - Macroeconomics (Jones, 2008)
Like new. $10 OBO

Econ 1A/1B - Economics (Taylor and Weerapana, ed. 6)
Good condition. $10.

Psych 1 - Pysychology (Gleitman, Reisberg, and Gross, ed. 7)
Like new. $10.

STS 101/101Q - Technopoly (Postman 1992)
Good condition. $5.

Interwrite PRS Transmitter
Works perfectly, batteries included. $20.