http://www.nctm.org/ - This supports teacher who are going into the field of mathematics. This website has useful resources, and helps you locate the standards you are trying to teach. I use this website often and have become a member for my professional development.
http://www.worksheetworks.com/ - This website helps you create your own kind of worksheets. You can customize the way your math problems look and even give an example of what you are looking for.
https://www.khanacademy.org/ - A great informational site for students to go to for free practice and video tutoring on any subject. http://www.corestandards.org/ - To go to when looking up common core standards in ELA and Mathematics