I know we already have a thread up for Japanese language/culture reference materials, but with the breadth and width of themes in the manga being assigned, I thought a thread about OTHER handy references might be in order.
Firstly, there has been a lot of flak about grammatical errors and the like in some recent releases. many times spellcheck wouldn't catch these errors as they were real words and spelled correctly, but were the wrong word (breath instead of breathe for example). Some were cases of the there vs there sort. While a final QC by a 2nd or 3rd pair of eyes would help, in cases where the grammar or spelling makes your mind go blank (happens to best of us when our brain just freezes), the follwing free online respurces may be of help:
This also has a thesaurus in case you need to find a diff word due to space constraints or preciseness.
And also, because we don't get to choose what we get necessarily, and many titles feature S and M which I doubt everyone is intimately familar with, for the sake of being able to get into the character's headspace and understand how something would be said in English during a scene and so on, esp. within the various forms of said BDSM (leather daddies, slave contracts, I could go on), I rec. the following as a starting point depending on your book's content:
http://www.amazon.com/Leathersex-Curiou ... 1881943054
http://www.amazon.com/Ropes-Bondage-Pow ... 868&sr=1-8
For this topic, I don't advise online resources as they tend to be inaccurate or fantasy sites and so on though if all you need is the right name for apiece of equipment then googling a BDSM furniture site should help as they have pictures of the equipment.
These books are well respected and researched, so should prove invaluable aids to making certain you fully grasp the content you are localising and therefore can do so accurately.
If doing yakuza related material, I rec. friending Jake Adelstein on twitter and reading his blogs and such. he has a list of additional reference materials that may be of interest.