Every time I introduce rubrics to a group of teachers the reaction is the same - instant appeal ("Yes, this is what I need!") followed closely by panic ("Good grief, how can I be expected to develop a rubric for everything?").
A good rubric can help students understand what is expected of them and it can help teachers score students' assignments consistently and efficiently. If your students are submitting assignments to you through Google Drive or Google Classroom, you may find yourself looking for a way to create and use rubrics without having to leave your Google Drive account to give feedback to your students.
With each Scratch project I assign to my high school students, I prepare a rubric. On one side, the project requirements are listed. These are generally listed in a short, bulleted list format which make them easier to follow.
How blogs are assessed depends on the assignment. You may assess each blog post (students respond to a given prompt) or you may assess all their entries together (students write regular entries without specific prompts, like a journal). Below are example rubrics for both types of blog assignments.
Another neat site that has everything from a rubric generator to educational games. There are several tools to help any teacher bring more tech into their classroom. I have only used one of them, so I am looking forward to seeing what some of the others can do.