When I just started translating fifteen years ago, I had my desk cluttered with all kinds of dictionaries, textbooks and handwritten notes from university lectures. Today, translators have all the world's knowledge within arm's reach — but not all of it is visible at first sight. Here are five of them that are not that famous but should be in every translator's toolbox.
Something halfway between a dictionary and a translation memory database, Linguee processes a huge amount of bilingual content, extracting and highlighting translations for the words and terms you are looking for. Although some usage examples contain obvious blunders, most of them come from reliable sources such as United Nations documents and can be trusted.
New Oxford American Dictionary via Google
A somewhat hidden feature of Google is that when you make a search for "define [something]", the engine automatically looks for matches in the New Oxford American Dictionary, arguably the most state-of-the-art dictionary out there. (Note: you should be using Google in English to do this.) It also puts a cherry on top by listing synonyms, showing the word origin in a nice and legible form, and plotting the word's usage over time based on Google Ngrams (see below).
If you ever find yourself stuck between several ways of writing a phrase or unable to choose between different options to translate a term, the Ngram Viewer is a translator's best friend. Based on the complete analysis of all Google books, it builds configurable usage charts for words and phrases (up to 5 words long). It also provides a number of research tools by allowing you to use wildcards to e.g. distinguish between different parts of speech.
Unless you are doing it just for fun, time tracking is a must for translators. It is the only way you can convert your per-word rate into hourly earnings and thus have a firm understanding of and control over the prices you offer to your customers. Having tried a multitude of time tracking apps, I found Toggl to be exactly what a translator needs. It is powerful enough to be able to manage multiple clients and projects, but not so powerful that you spend more time tracking time than working.
Finally, a piece of software for translators whose development I'm proud to have a hand in. Despite being a SmartCAT employee, I believe I'm qualified to post this here, as for one year before joining the team I had been extensively using SmartCAT in my translation practice. From being completely free to having a multitude of built-in CAT features (translation memories, glossaries, multi-stage execution, quality assurance, you name it) to providing an open marketplace of translators, SmartCAT is the IKEA among CAT tools, covering 90% of my translation workflow.
That was my list of "hidden in plain sight" tools I use for translation. What about you? Do you have some secret knowledge to share?