SBS stands for Shitsumon o Boshuu Suru, which translates to, "I'm taking questions". First started in Volume 4, Eiichiro Oda continues to devote a couple pages in each One Piece tankoban to fan mail sent in by dedicated readers. The subjects addressed vary across a wide variety of topics, from curious occurances within the manga to jokes and even French Bread. Oda's responses in his SBS are very casual, and are vividly infamous for dubious or outright silly responses.
Organization
In Oda's own words,
+Well, finally, here is the SBS corner I announced in volume 2. Thank you for sending all of your letters.
+To answer the readers' questions as easily as possible, I will use "D" (Dokusha = reader) for the question and "O" (Oda) for my reply. I will pick from the collection of letters and postcards at random.