Automatic Thresholding using Histograms

Anybody know of an algorithm that will help me identify peaks in a histogram?

What about an automatic thresholder algorithm that could calculate the threshold by looking at the boundary between two peaks?

I am also looking for a reference source that describes the technique of using a percentage of the cumulative histogram to calculate a threshold. In this algorithm, I want the software to analyse the stack of pics and determine the percentage to apply to the cumulative histogram.