The NCTM website is one everyone is familiar with; there are a lot of resources here that are great for explaining concepts. This is an interactive activity working with vectors to help students understand basic facts about the difference between magnitude and direction.
This set of applications lets you set up audio drop-boxes so your students can record and turn in their spoken answers. There are also ways to create worksheets for videos and embed them together in a "mash-up" activity. Especially for foreign language teachers, this seems like an awesome assortment of apps!
Lessons, interactives, calendar activities, and more, right at your fingertips.
Read write think is a great resource for lesson plans but also has many types of free templates available for graphic organizers. I have primarily used read write think for brainstorming in the classroom as many of their organizational templates are great accommodation for visual learners or students who really benefit from structure.
This is a great math site. It includes sections for activities, lessons, standards, and web links. The activities and lessons are grouped into grade levels to facilitate your search.
This website contains flashcards and games to help students improve their math skills interactively. It also contains worksheets that students can print and work on. The website also has the answer sheets so students can check their work. There is also a "homework helper" tab that allows you to input your problem and answer and it will help you figure out if you are correct.
Annenberg Learner Interactive website that covers many content areas, including math, science, history and language arts. This site has many layers to it with lessons for upper elementary through high school, and a video library for teachers.
Khan Academy is like your very own digital tutor. This site has a ton of educational videos and interactive exercises (particularly in math) that cover skills that range through grades k-12. Students, teachers, and parents alike can learn an abundance of things from Khan Academy, and it's completely free.
IXL has hundreds of Math related games, categorized by grade and topic. It is a subscription based site, but allows quite a few free uses, and even once you've used up your free practice for the day it refreshes and let you try again the next day.
IXL is the world's most popular subscription-based learning site for K-12. Used by over 5 million students, IXL provides unlimited practice in more than 4,000 math and English language arts topics. Interactive questions, awards and certificates keep kids motivated as they master skills.
Interactive math manipulatives that make math concepts come alive. Thinking Blocks teaches students how to model and solve math word problems. There is even a Thinking Blocks, Jr. which caters to 1st and 2nd grade students. Admittedly, Kathy recommended this website to me when I asked her for suggestions that might help my 4th grade daughter who was struggling with fractions. My daughter loves it! Thanks, Kathy!