Thanks for the suggestions; I'll check them out.
The project started when I was trying to find resources for my gifted DD 10. Since the book is for students in a public school, I try to offer resources for students who find math challenging, typical students, as well gifted children. The reason I came here for help is that I find the best resource suggestions come from parents of gifted children.
I'd appreciate any resources you can suggest. I try to describe them in the book based on the age-level they're aimed at; then parents can adjust. For example, parents of gifted kids in k-3 find the 5th and 6th grade materials useful. Some resources appeal to all ages and levels; for example, the most popular resource listed in the book by far is Minecraft.