Useful Drupal modules

Click on the module name for notes, comments, patches.
Recommendations (for and against) are my personal opinion only and may be out of date. Feel free to email with corrections/suggestions.

Why haven't you mentioned Drupal 9? As of December 2021 I've updated most of the sites I look after to Drupal 9 (experience: mixed). I haven't decided how to label future version compatibility as D10 will be coming soon as well. The upgrade_status module is superb. You're bound to have issues with composer. Also watch out for a nasty session headers bug with redirect_after_login.

(1 modules in list)
Module name or machine name
Any text in the notes
Name D8 Personally Tested Last Updated
reCAPTCHA (recaptcha) 2020-02-10

d.o. page

"Essential"

Use in conjunction with the Captcha module to prevent spam on forms.
As of Jan 2020, still ONLY supports v2 of Google's reCAPTCHA API (there's an active issue for v3 support)
There's also an option for non-js fallback.

Tested with D7 and D8.

Patch needed for AJAX forms (e.g. Webforms with AJAX support turned on) to stop the ReCAPTCHA UI disappearing when page is reloaded.