A great web site that I have used this year is explorelearning.
This site has many excellent lesson resources for both math and science. It requires a paid subscription to be used freely, however it allows users to get a 5 minute free pass to interact with some of their "gizmos", the applications that illustrate a wide variety of math and science concepts.
In the last week I have used this website for both math and science. Students have reinforced their understanding of multiplying fractions by using the gizmo. Making a work sheet to go with the gizmo helps to add structure to the lesson. Students get their laptops, log in, then gather around the front of the room where I take them through the activity on my smartboard. After ensuring that they are clear on the goals, procedure, and flow of the lesson, they head back to their computer, search for the desired lesson and then begin to work at their own pace. Worksheets are provided for each lesson; however I sometimes make additional worksheet questions that may be suitable for differentiation (in particular for ESL learners).
Students have reinforced their understanding of distance-time graphs by using the explore learning gizmo for this activity. Kids were able to manipulate a number of variables (distance, time, number of runners) while constructing a distance-time graph, and then observe the impact of this of on an animated figure as it runs under the graph they have just created. The activity itself is very engaging; it is also possible to stimulate discussion/challenges by having kids write a set of instructions that other students have to translate to a graph, and ultimately the cartoon figure.
A further plus for this site is that under each gizmo, the page has a short test that quizzes students on the main ideas that should be taken from the lesson. Once completed, the students can check their answers for immediate feedback.
The positive reviews students give to me with regard to explore learning means I will continue to use (and adapt) this piece of technology to further student learning.