A Taylor diagram is a plot that shows the similarities of different models with respect to a given data set (correlation and RMS). It seems to be mostly used for climate models, but I've never seen it in action in astronomy fields.
I made a python/numpy/matplotlib implementation, which was then used by Michael Rawlins (from Univ. Massachusetts) to produce plots to be published in Rawlins et al., 2012. Assessment of regional
climate model simulation estimates over the Northeast U.S., Journal of
Geophysical Research (in review).
N.B.: do not trust this illustration for (geo)scientific purposes, but refer directly to the published version of the plot if needed.