This is one of my favorites.
This is the site with the great number line tool for all operations. Many other tools are offered for grades k-12.
Print a complete set of cards 0-9 on two pages.
This site allows you to set specific parameters to meet standard and differentiated student needs. Click home to go to other subjects.
This balance works just like the manipulative ones in your classroom. It's great for demo.
Copy into notebook software with the capture tool.
This site has blacklines organized by grade level.
John Van De Walle
This site contains links to PDFs of the blacklines mentioned in John Van De Walle's Teaching Student-Centered Mathematics series.
This site offers a wide variety of printable blackline masters for manipulatives, tables, etc.
Build or find rubrics. I suggest building rubrics with students.