I’ve found some interesting schematic of load cell amplifier. As we know, load cell amplifier is pretty expensive with fair price range of 100-300 USD. You may built your own load cell amplifier to get the lower cost. Here the two scheme diagram of load cell amplifier circuit:
Load Cell Amplifier using AMP04:
source: http://cgi.ebay.com/Load-Cell-Amplifier-Improved-Better-Stability-New-/350451149452
Load Cell Amplifier using INA125:
source: http://www.aircommandrockets.com/day67.htm
source: http://psas.pdx.edu/LoadCellAmp/