The following are screen shots of online math worksheet websites I use. The variety and the options in the criteria you select for your worksheets for some of these sites allows for differentiation in the classroom.
I will start with my favorite site, Math-Aids.com. This site allows for dynamic selection of criteria for each handout (see 2nd photo below) such as choosing the types of coins in problems for counting out the total value. The coin images are outstanding! It also offers content up to Calculus.
Super Teacher Worksheets is often used elementary schools. It offers content in science and language arts as well. It requires a $25 annual subscription which I easily find to be worthwhile.
Common Core Sheets is very useful site if you want to find handouts for specific standards by grade level (see 2nd photo below). It offers multiple versions of each handout.
Dads Worksheets provides a large bank of worksheets – multiple versions of each worksheet.
Math Worksheets 4 Kids offers multiple versions of each worksheet and content in science and language arts. There are many worksheets that provide unique support in how the work is presented, e.g. the Ratio Slope worksheet shown in the 2nd photo below.
Visual Fractions – title speaks for itself.
Worksheet Works is my 2nd favorite. It offers options in the criteria you choose, e.g. difficulty level (2nd photo below). They also offer unique types of handouts such as a maze with math problems to solve to find the path (2nd photo).
I wrote in another post about a 7th grader with asperger’s who tested in math at a 1st grade or kindergarten level. I used scaffolding to show him how to do Sudoku puzzles. On the left is a simple version with one digit missing from the box. In the middle is a little more complicated scaffold. On the right is a completed Sudoku puzzle that this student completed on his own (minimal prompting). These worksheets come from http://www.superteachersworksheets.com.