An Intuitive Guide to Linear Algebra : An more-visual explanation for linear algebra; part of a series on an intuitive understanding of mathematics (I chose this one because it was recommended by others interested in the topic)
The Map of Mathematics: interactive website showing the connections between types of mathematics, an introduction of each branch of mathematics, and more articles to read
Match the Net: a single-player game about 3-dimensional polytypes where you will meet the five Platonic solids and their friends