I need a way to connect 6-8 voltmeter boards I'll be building myself to a microprocessor that can parse the information from the meters and run a program like "if voltage from voltmeter A is > preset maximum voltage, turn off the power and turn on a little red warning light." Any ideas?

 

Why not use a uC that has a built-in multichannel DAC, and just use that? Not precise enough for you?

 

That would work. Any ideas on specific models/specs and how to connect everything?

 

There are lots of uC's available from many manufacturers.

Microchip's PIC uC's are pretty popular, so are Arduinos. Parallax Inc's Basic Stamps are easy to program, but quite pricey.

First, you need to detail all of your requirements for inputs and outputs.
That is what will eventually narrow down your choice of uC's.

With Microchip's PICs, you could get started with a PICkit2 Debug Express kit that comes with a 44-pin PIC16F877 uC on a board, for about $50 US+shipping. The PIC16F887 is an 8-bit uC that has a software-selectable clock speed from 31kHz to 8MHz, and has a 14 channel 10-bit DAC, among many other features.

 

If it's only one preset level per case, a few voltage comparators can work, too. A low means below setpoint - high if above.