This list is a bit more dev tool focused with a recommendation on a book by a great startup with Irish roots.
If you work with CSV data at all as part of your job then CSVKit is a very flexible tool to have at your disposal. Its been a real time saver for me on data migration projects and general data wangling. CSVKit requires Python 2+ and is a installed easily via pip.
In a similar vein to CSVKit I quite often find myself using NimbleText to quickly transform chunks of text data from one format to another. It comes with lots of patterns out of the box or you can simply create your own. Think tasks like generating SQL statements for a delimited list of data, reversing lists of data etc. NimbleText has free Desktop, Pro (Paid) Desktop and free online versions - I find I can do most of what i need with the free online edition but the Pro does add quite a few nice features.
Its easier than ever to get distracted when you are trying to be productive - News, Netflix, Facebook, WhatsApp, Twitter, etc all just a Chrome tab away.
RescueTime is a little app that will keep records of what you are spending your time on and give you a weekly report outlining the details. You identify apps, activities, sites etc as productive or otherwise and let RescueTime show you if you are getting distracted or being as productive as you set out to be!
How often does a new member start your team and have to spend way too much time setting up their dev machine with required software, development environments, settings etc? The same old problems and gotchas over and over.
GitHub opened sourced their development environment automation tool Boxen which solves exactly this problem. They've provided a starter template that you can take and refine or throw away altogether. You could certainly roll your own tool but Boxen provides a great headstart.
Since being founded 6 years ago in San Francisco by 4 Irishmen, Intercom has become one of the fastest growing startups in Silicon Valley. Its easy to see why with the quality of the founding team and staff they have attracted from companies like Facebook, Amazon, LinkedIn to name a few.
In Intercom on Starting Up they round up their best articles from over the past 6 years and current thinking into a single book. Topics include Product Design, Engineering, Culture, pricing, competition and many more. Its a great read with some great insight into how they've managed to get to where they are today.