Well of course being a member you can comment, create, develop, seek advice and give advice on warcraft 3 related material.
Aside from that you can just enjoy being on the forums and having a place to talk about various things.
Also you can compete in various types of contests like Mapping, Modelling, Terraining, Music Composition and Concept Art.
Now that that's out of the way, sit down, relax and enjoy your ride/stay.