As far as a full colorimeter set for under 100$ with the colorimeter and decent software, I am hard pressed to recommend anything that exists.
The cheapest 'kit' I think would be a useful investment is this...
http://www.bhphotovideo.com …_Colorimeter_Monitor.html
though I muuuuch more highly recommend this kit
http://www.bhphotovideo.com …98930&Q=&is=REG&A=details
yes, its about 140$ more, but is it going to be worth it in the long run? I have 0 doubts that it would be for you.
One question you have to ask yourself is, why is color accuracy important to me? How important is it to me? Do I do alot of printing?
These questions require answers and those answers will help lead you to the colorimeter kit for your needs.
I hope that at least one of your screens is a nicer panel and not TN...
If the monitor panels are TN based LCD, calibrating will not be very effective due to the nature of a tn panel. If you have say a pva, or sva, or ips panel, then you are in luck. These panels will provide you much better color accuracy, and uniformity throughout the screen as well as better viewing angles.
Either of the products I had listed are very good products. The cheaper being quite good for the cost, though the newer more expensive device, well, is just a bit more accurate and worthy of the upcharge.
Just my .02c hope it helps