Software tools for WCA competitions
This page is a non exhaustive list of tools which are known to be used to help with the organization of WCA competitions.
Not all tools on that page are maintained by the WST: it's definitely fine! We don't have the manpower to manage all the WCA-related software out there :)
All the programs on this list have been used during real WCA competitions and integrate with the WCA website: they let you sign in with your WCA account to be able to import (and sometimes update) your upcoming competitions data. For each of them the maintainer(s) will be clearly written.
Before the competition
Managing competitors registrations can be done directly on the WCA website. Since managing groups and staff manually can be time-consuming, you may want to consider using one of the tools below.
Groupifier
Task and group management tool for WCA competition organizers. Among the main features you will find: sorting competitors by rankings, assigning tasks (judging, scrambling), deciding how many scrambles are needed, generating score sheets, personal sheets, and summaries... Check out the website to find out more.
Sources (Jonatan Kłosko)
During the competition
You will find here tools that let you manage the results of the competition while it's going on.
Results spreadsheet 
Sometimes things happen... If you don't have network access, you will have to use the good old spreadsheet.
After the competition
While results validation occurs right there on the website, you will have to use some tool to assign scrambles generated by TNoodle to the actual results submitted to the WCA website.
Scrambles Matcher
Can be used to assign scrambles generated by TNoodle to results. Import results from the WCA website (when using WCA Live), a spreadsheet, or a standalone WCIF file. Import scrambles from one or more TNoodle json file(s). Export results to the appropriate format for WCA submission.
Sources (WCA Software Team)