I found this link while digging around trying to find out what happened to Helena Verrill’s site(s). it’s for Ralf’s Origamipage, at http://www.origami-online.de/index_de.html.
Take a look at his tessellations- some of them are very, very complicated pieces of work! quite stunning. I really like all his folding with triangular creasing, as I think that the triangle/hexagon combo is really the way to go for great tessellation patterns.