I picked up some of these Texas Instruments "self-calibrating", dual high precision op amps, TLC4502AC -- 8 pin surface mount -- they have a ADC and DAC built in to "set and forget" offset upon power up -- $1 -- usually $3.80 - $4.16 ea at DK.
spec sheet is here:
http://focus.ti.com/lit/ds/symlink/tlc4502a.pdf
jack@tech-diy.com
spec sheet is here:
http://focus.ti.com/lit/ds/symlink/tlc4502a.pdf
jack@tech-diy.com