The Tex Murphy games are all 30% off at GOG this weekend (and only for the weekend).
http://www.gog.com/en/page/tex_promo/
Mean Streets and Martian Memorandum are a little over $4 as a result.
Under a Killing Moon, Pandora Directive and Overseer are $7 each during the sale.
The Overseer release is the CD version rather than the superior video quality of the DVD version though due to troubles getting the DVD version working well and avoiding a game stopping bug that only effects the DVD version.