The subject area that you are looking for is called non-photorealistic rendering. It is currently an active area of research in computer science having many, different branches of study.
I did a quick search for "crayon rendering" and found a paper, "A bidirectional deposition model of wax crayons", that has example images.
You likely will not be able to find an RIA/JS software package for rendering an object as if it was drawn with pencil or crayon (not just using Photoshop filters) without implementing the techniques in research papers yourself. The graphics at the site that you linked to were probably hand-drawn by an artist who used a graphics tablet.