Some good thinking questions here. The couple I have looked at would be great at a grade 9/10 level

Good Fractions practice - quite basic to quite advanced with good visual aids.

Some good interactive graphical illustrations for calculus. I especially like Average and Instantaneous Rate of Change

An incredible resource! 68 lessons from functions (a touch of grade 11 but mostly grade 12) to university calculus. Tons for MCV. Make sure to link to this from your moodle!

An interactive demonstration of orders of magnitute

An amazing resource for non-linear physics research. Gravel roads to stalactite formation to pouring syrup - physics (and mathematical) analysis all here

Support information for washboard road sinusoidal analysis

Lesson plan for analyzing sinusoid patterns in gravel road washboard patterns

A great resource for line art. Lots of mathematical shapes and diagrams.

Cute (and effective?) intro for conditional probability

An online graphing calculator with great visual presentation. Nice thick lines for projection. Implicit graphing. Easy tracing. Mulitple functions (and relations!) graphed at once. It looks like this tool is under ongoing development, and a committment to remain free. This one is a keeper.

A great site - essentially an interactive textbook for Grade 9 Alberta curriculum. Lots of java applets presented within written passages set up to lead through a progression of knowledge/skills. Resources for a number of other courses if you hit the [Home] link at the top of the page, but I have not looked through other areas of the site.

Stats Can data sorted by the type of relation it approximates - linear, quadratic, logs, sinusoidal, exponential, cubic, combined,

Great task-based (and test) assessments! Emphasizes mathematical process expectations like communicating, reasoning, selecting tools, etc. Free to use unmodified. Primarily up to grade 10 level. Sorted by americal Common Core Standards.

Timon Piccini's video resources based on Dan Meyer's 3-acts format. A good fit for both inquiry and authentic learning approaches. These videos fit well for Grade 9, and some stats ones are on the way (available now via his Vimeo channel)

Visual models (both circle and bar) for equivalent fractions, and operations with fractions. Only draw back is that mixed numbers are used exclusively rather than improper fractions also.

Graphs of different types of data broken down by topic. Could be used to discuss representing (and misrepresenting) data in MDM, graph reading or percents and ratios in grade 9 courses

This site traces the origins of many mathematical words and symbols It cites sources rigorously and appears highly reliable.

These missing comma examples might be used to talk about importance of brackets in expressions to clarify meaning.