I'd like to invite you to a math problem-solving website I wrote called Math Spies. I started it more than three years ago, but then took a break that ended up being over a year.
Last year my students were using it and started clamoring for more problems. The first problems took longer for me to write and post than it did for my students to solve. I decided to make a change in format.
I plan to do a question a week each Wednesday morning for the school year. I just completed a set of questions about probability called The Case of the Corrupt Carnival.
I moderate comments for websites I use in my own classroom. I do read and post relevant comments.
I'd love to have you try the problems with your students and let me know what you think. It's free.