I've done some Bootstrap projects in the past but I felt like I needed a refresher, so I've been working through a Brad Traversy class on Bootstrap 4 and posting the finished projects on my github.
LoopLab - The first one was a one-page, responsive site that utilized a sticky navigation bar, a fixed background in the top section for a parallax-type effect, various types of buttons, and a form. All pretty standard fare but good to freshen up the skills. Version 4 of Bootstrap does include FlexBox so it was good to see how it is used within this site.
Glozzom - The next one was a multi-page project. It made use of a carousel in the top section, Cards, another carousel with quotes, an embedded video in a modal window, and some more fixed background parallax effects. It also uses the accordion feature in a FAQ section as well as some more practice working with forms. I almost forgot it has a image gallery feature where you enlarge the images into modals.
Mizuxe - Another one pager, this one was mostly more of the same. Responsive, more forms practice, an accordion to show/hide bios, and smooth scrolling to different parts of the page.