  In this article, I give a pedagogical introduction and overview of
percolation theory. Special emphasis will be put on the review of some of the
most prominent of the algorithms that have been devised to study percolation
numerically. At the central stage shall be the real-space renormalization group
treatment of the percolation problem. As a rather novel application of this
approach to percolation, I will review recent results using similar real-space
renormalization ideas that have been applied to the quantum Hall transition.
