Texas Education Agency - Have a number of resources on student assesments, including reading, writing, science, math.
US Dept of Education - Lots of material on how to improve scores and accurately assess.
NETSSA - Assessment of 8th grade level pdf file.
Middle States Commission on Higher Education - Pdf file on student assessment. Lots of information, but more theory than practical use. Have to sit down a long time to get it.
Illumination - Standards in Math at varying levels.
Lesson Plans.com - Tons of material regarding lessons, worksheets and rubrics. It’s free but hard to navigate.
Teacher Planet - Grading Rubric for lots of different subjects.
Teacher Vision - Rubrics Library with lots of different subjects. Have to log in to get most of them.
Teachnology - Lots of resources for worksheets, lessons, and rubrics. It’s fairly basic but offers some good material.