This handy infographic by FastPrint would help you pair Google Fonts in a breeze.
The cross-reference chart contains a total of 400 unique pairings, labeling them under color grids—the white square indicates that the font would work well together, the grey ones represent an unlikely combination, while the black indicates that the combination should be avoided.
Scroll down for a closer look at the infographic.
Click on image to enlarge
Click on image to enlarge
[via CreativeBloq, FastPrint]