i found this reAnimator tool via alpha, for visualizing how regular expression engines use finite-state automata to match regular regular expression patterns against text. it's really cool and the explanation was made in openlazzlo. The regular expression is compiled into a nondeterministic finite-state automaton.
i like the a/ab/abc/abcd example and the a*b/b*a examples the best. check it out. it's actually quite fun to visualize. i wonder if you could build on this theory to expand it into a blog platform and use it to link words and tag items, link posts, and advertizing.