This is a wonderful resource. I have been floundering to find a topic for the 5000-word middle-grade historical adventure/fantasy story with the theme of voyagers for the forthcoming Insecure Writers Support Group anthology. Click the link to find out more details if you'd like to participate. The deadline for entry is September 1.
I had already written one piece, but it was too mature and quite too dark.
If, like me, your understanding of the difference between middle-grade and young adult isn't entirely clear, do read this post. It will help clear up the confusion.
Disclaimer: I am not an affiliate or employee of Writers Digest. This is an honest, uncompensated recommendation of a post which I found helpful.