Bootstrap Magic - Create your Bootstrap 4.0 themes easily with magic
Rainglow Color Themes - 320+ color themes for a variety of editors and software.
HackerThemes - Bootstrap 4 themes and tools for web developers
Slack Themes - Make your Slack pretty with custom themes
Bootstrap 4 Cheat Sheet - An interactive Bootstrap 4 cheat sheet
eM Client - eM Client is a fully-featured email client for Windows and macOS with a clean and easy-to-use interface. eM Client also offers features for calendars, tasks, contacts, notes, and chat.