The best tools are those that you never notice, those that work entirely in the background to make your life just a little bit easier. Keeping that in mind, I’d like to recommend azmanam’s chemistry dictionary, which I’ve been using for the last three years or so . It slots into MS word, Libre Office, etc. and convinces your computer that benzene, taxol, di-tert-butyl-dicarbonate and all the rest are real words, making spell-checking a lot easier. At a little over a hundred thousand words long, the dictionary has virtually every chemical known to man, save only for those that you discover.
The dictionary is free. Get it here.
 The dictionary is a victim of its own success, in a way. I would have written about it earlier, but I only just remembered that I was using it.