Voltage range shifter from 0V to 3V to -/+1.5V
This is pretty similar to Andy's (already selected) idea, but implemented with an op-amp and TLV431 low-current reference. R3 biases the reference with 0.2 to 0.5mA. The TLV431 series impedance causes a small gain error of less than 50ppm. R1 and R2 establish the reference as about 1.5V (use the 'T' grade device and 1% or even 0.1% resistors if you want high accuracy (and calculate them more accurately than I did, including typical REF current). 







simulate this circuit &ndash; Schematic created using CircuitLab