Bootstrap 4 Cheat Sheet - An interactive Bootstrap 4 cheat sheet
Short.io - Short.io makes short links (vanity urls) on your own domain. Free signup, analytics and API. Chrome, slack, zapier and segment integrations.
Bootstrap Zero - Open-source, free Bootstrap templates collection.
PixelMe - URL shortener for savvy marketers
HackerThemes - Bootstrap 4 themes and tools for web developers
Cutt.ly - Free custom URL Shortener and branded URLs with advanced links tracking and Link Management Platform & API.