You can find a loose collection of useful tools not coded or maintained by Neverwinter:Uncensored here. Check them out, they are great!
DrunkenMMO offers a basic function where you can set up reminders for your professions and / or auctions bids.
In my opinion, personalizing your Aliases and Keybinds is the best QoL improvement available to enhance your gaming experience. Setting things up seems daunting, but it's an investment in a faster and more intuitive future for yourself. Besides, if you keep reading you'll see that it's just a couple easy steps.
This project allows you to place and label markers on pretty much every available adventure map. That way you can create and share interactive maps that help fellow players to find certain locations on maps.
A page full of general theorycrafting, useful info and some tools. Has a slight focus on Trickster Rogues. Check it out!
Google spreadsheet to calculate Stronghold progression.
Sharpedge's CW bible formerly known as Almost Everything Guide.
A visual side-by-side comparison of the colors of three dyes.
List of all dyes that's sortable by luminance and hue. Great to find the darkest available dye in example.
The tool lists every possible Insignia Bonus combination for the Insignias you own.
From the biggest egg-shaped heads with the brightest minds at Unrepentant Gaming comes the Stronghold Calculator. This tool is designed to help Guild Leaders (as well as peons who know math good) to calculate the costs to upgrade their Strongholds, as well as how much specific buildings cost.