One application that many people try to build is an Altimeter. While I applaud anyone trying to build this circuit, there are circuits out there that have already have a proven history.
Todd Owen is an application engineer at Linear Technology and in 2002 used the NPC-1220-015A-3N pressure sensor to make an altimeter for enthusiasts wanting to know altitude changes from an initial elevation. This circuit uses a single cell, 1.5 battery and a LT1307 to operate. The LT1490 is used to set the drive current for the pressure sensor and the LT1167 instrumentation amplifier to set proper gain to drive a simple 4 1/2 digit LCD display. Todd actually tested this circuit in a De Havilland DHC-6 Twin Otter airplane!
Another application engineer for Linear Technology, Mark Thoren came up with a good circuit in 2005 which was published in a Linear Technology application note 96. This circuit uses the NPP301 pressure sensor and LT2411 ADC to achieve a 3% for 10,000 altimeter. In addition this application note also includes the SPI code to log the data into a PIC.
If you have a schematic you would like to share, please feel free to send it to me at scott.weatherwax@cdiweb.com