AVR-Chat

>
>any suggestions on what to use for an external ref ?

Any convenient band-gap chip will work. In my case, I used the 4.096V version.

>I used a TI chip, the TLS2543, 11 channel 12 bit ADC chip and also
>found that unless the actual Vcc was corrected for, there were errors.
>
>The guy who I was working with put a 0.01uF to ground on each input
>as a means to reduce the noise.

In general, you should filter out anything above the sample rate.
You can't really select a cap value without knowing the source impedance.