Complete Walkthrough with screenshots and SideQuest Guide!
http://pokedream.com/games/diamondpearl/walkthrough/
Complete Walkthrough with screenshots and Game Mechanics Information Including Pokemon Natures and Berrys Information, and Shinnoh "Shinou" Pokedex Listing.
http://www.pokemonpalace.net/?id=nds/dp_walkthru
User-Contributed Wiki of Pokemon Diamond & Pearl Game Guides & Walkthrough
http://strategywiki.org/wiki/Pokémon_Diamond_and_Pearl
Italian Pokemon Diamond and Pearl Walkthrough
http://www.charizardpage.com/dp/
Hosted Game Guide Walkthroughs and FAQs
http://www.gamefaqs.com/portable/ds/game/925601.html
http://neoseeker.com/Games/Products/DS/pokemon_diamond/faqs.html