I’ve recently added Dresden Codak to the list of webcomics that I read regularly. It’s a wonderfully bizarre and twisted mixture of science, philosophy and religion geekery; Egyptian gods having trouble with Schrödinger’s cat, an RPG based upon philosophical arguments, working in a dream world, and and a guide to “traversing the luminiferous aether” are a few of the highlights. The most recent ones have fantastic scripts and art, with particularly interesting layout and colour.
My personal favourites are Dungeons and Discourse and Summer Dream Job.