Long-term Formative Feedback Tools?

I'm working with a group of 9th-grade teachers who are focusing on improving their use of formative feedback. They would like to use technology to help them deliver meaningful feedback to students.

They're looking at two types of feedback: immediate and long-term/progress over time. I have some ideas for them -- Poll Everywhere and Wifitti for immediate feedback, blogging for long-term progress over time. But I'm looking for more.

What ed tech tools are you using to help give students formative feedback? (I'm especially interested in free tools.) Thanks!