GraphFree may well be the most useful website to present graphs in your work. This is a very functional tool as it can be used to graph various functions (including piecewise and trigonometric). There is a tutorial on this site to help you with this.
Math Open Ref hosts a variety of animated tutorials for common mathematical terms. A key piece is the section on constructions. It takes constructions step by step or as a continual process. It is very comparative to watching someone perform live constructions.
PatrickJMT hosts a large volume of tutorial videos covering 100's of math topics ranging from early mathematical topics through post-college material. I highly encourage students to check here when they need a bit of help.
The GeoBoard site will serve various functions - ranging from shape design to determining the lengths of square roots. The ability to utilize colored bands (unlike most personal geoboards).
Math.com has resources ranging from tutorials to vocabulary practice. Please be cautious for they do support themselves with external links. Alas, the tools are worth the navigation.
coolmathgames is a collection of fun games - many of which 'teach' mathematical concepts.