Composer is useful but can be more with plugins, but there are no list about them so this is mine.
This plugin improve the speed during the downloads on the modules using a parallel system: https://github.com/hirak/prestissimo
Keep the modules updated in your installation can be a boring process but there is a plugin for that: https://github.com/Soullivaneuh/composer-versions-check
It displays some texts after each Composer update to nicely summarize the modified packages with links to release and compare urls. https://github.com/pyrech/composer-changelogs
It displays desktop notification when Composer finishes install/update commands. https://github.com/pyrech/composer-notifier