Senao (Rebadged by Engenius in the US) makes Prism 2.5 based cards that are 200mw with excellent receive sensitivity. These work great with the hostap drivers under linux and are the recommended cards for doing any sort of distance links. As an added bonus, they work great for wardrivers too
They come in two models, one with 2 external MMCX connectors and no internal antenna, and another with internal antenna only.
http://metrix.net/metrix/products/radios/pcmcia