How far along is the anime compared with the manga? Episode 596 came out today, and I am having a hard time placing this in the manga's time-line. 

Around which chapter would the anime be right now? And would watching the anime spoil the manga for me?
If you want to start reading the manga from where the anime is right now, the last thing you see in the anime is Luffy grabbing Caesar (episode 597), which corresponds to Chapter 670, page 19.



The last manga chapter right now is Chapter 709 (710 will be coming out either today or tomorrow), so the anime is about 40 chapters behind the anime.

If you translate it into arcs, the anime right now is in the Punk Hazard Arc and the manga is in the Dressrosa Arc.