I get things for my fifth grader on teachers pay teachers - sorry IDK the url at the moment! - but that's the name of it. You have to register, but many of the items are free. I've even paid for a few ($1 - $3, things like activities to go along with literature she's reading).
For project-based ideas she loves using DIY.org - I highly suggest that. The kids can create things and post them, in a safe environment, but also they can earn "badges" by completing various steps in learning how to do something and posting about it. It's free.