This is an Arduino library for the BMP085 barometric pressure/temperature/altitude sensors. 

Pick one up at http://www.adafruit.com/products/391

To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder BMP085. Check that the BMP085 folder contains BMP085.cpp and BMP085.h

Place the BMP085 library folder your <arduinosketchfolder>/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.