Startup Rocket By Buildily - The best startup tool kit for founders in one membership
Now UI Kit - A beautiful Bootstrap 4 UI kit. Yours free.
JumpStart Toolkit - A pack of tools and goodies to jumpstart your startup
Module 02: Layouts - Professional toolkit for UI/UX design
Startup Toolkit - Interactive how-to guides to launch your startup
ArchitectUI - Modern dashboard template for bootstrap 4