The ones that I've looked at and liked are Free Calendar Widget and Month Calendar Widget. (Sorry, I can't post links, yet.)
I've searched here and on Play, but haven't found anything that fills my needs. I'm looking for a small (1x1, 1x2, 2x1. 2x2) calendar widget that just shows the month grid in a clean and simple way. I've looked at a couple of apps, and found them quite nice, but not small enough.