We present a new set of secondary standard stars for the u'g'r'i'z' photometric system that has been established in selected open and globular star clusters. These standards are calibrated to the original standard system defined by Smith et al. with an accuracy of 1% or better, extend as faint as r'~20, and are concentrated in small regions of the sky. As a result, they can serve as viable calibrators of photometry obtained on some of the large-aperture, high-demand telescopes that employ the u'g'r'i'z' filter set.