Petrifying propositional logic. And pretty solid explanations all the way through. Start. or home page with large graphic Good graphics and explanations. But can take a long time to load. Also has examples of both kinds of arguments.
Proofs are ok.
Good use of colour and small graphics. Interesting backgrounds without being too intrusive. Some are a litttle too cryptic to be good explanations. The arguments are good, but readers would benefit from having the raw material there also. Start Some good links out.