Vivus is a lightweight JavaScript class (with no dependencies) that allows you to animate SVGs, giving them the appearence of being drawn. There are a variety of different animations available, as well as the option to create a custom script to draw your SVG in whatever way you like.

"Raphaël is a small JavaScript library that should simplify your work with vector graphics on the web. If you want to create your own specific chart or image crop and rotate widget, for example, you can achieve it simply and easily with this library."