I think that for teaching geometric solids, 3D models work better than flashcards, which are two-dimensional. I used the free printables on this site:
http://www.senteacher.org/Worksheet/12/Nets.xhtml, printed them out on cardstock, and made the models with some "help" from my toddler. Then, I made labels in English and Chinese and play a game with her where she matches the names of the geometric solids to the models.
By the way, we also love Peter Weatherall in our house! Ella easily learned the concept of greater than/less than with the help of McGreedy the Alligator. Although, according to her, "He is not really greedy. He is just VERY hungry!"