http://www.kutasoftware.com – This site offers skills-based practice for Middle School and High School Math.
http://www.mathcounts.org – This site build problem-solving skills by allowing students to engage in fun, relevant word problems.
http://www.artofproblemsolving.com – A more challenging problem-solving site for accelerated students.
http://www.khanacademy.org – A site with video-based tutorials by skill.
https://www.engageny.org/resource/new-york-state-common-core-sample-questions - A site with the released State Exam questions from last year
http://www.nysedregents.org/algebraone/ - Past Common Core Algebra I Exams with solutions