Mega Menu (edit)
https://pluginarchive.com/wordpress/megamenu
http://www.designerslib.com/bootstrap-mega-menu-templates/
https://designmodo.com/demo/css3megamenu/
http://designm.ag/inspiration/mega-menus/
https://code.tutsplus.com/tutorials/how-to-build-a-kick-butt-css3-mega-drop-down-menu--net-15129 (HAY)
More:
https://www.w3schools.com/howto/howto_css_mega_menu.asp
https://www.leotheme.com/guides/prestashop17/leo_megamenu/
https://www.jqueryscript.net/menu/Simple-jQuery-Drop-Down-Mega-Menu-Plugin-Mega-Menu.html
https://www.jqueryscript.net/demo/Creating-An-Accessible-Mega-Menu-with-jQuery-CSS3/
Responsive Menu
https://www.jqueryscript.net/menu/Mobile-friendly-Sliding-Mega-Menu-Plugin-jQuery.html
https://www.jqueryscript.net/menu/Lightweight-Pure-CSS-Mega-Menu-For-Bootstrap-Yamm.html (HAY)
https://www.jqueryscript.net/menu/Responsive-Cross-platform-jQuery-Mega-Menu-Plugin-megamenu-js.html
Dropdown Menu
https://css-tricks.com/solved-with-css-dropdown-menus/
http://jsfiddle.net/kkobayashi/y0tfuqxo/7/
https://www.bootply.com/testazoid/bThTHo2fgG (Dropdown open in right)
Bootstrap Grid 5 columns
https://codepen.io/DenisDov/pen/pyjpgP
https://www.uakron.edu/it/cms/responsive-guide/gridding/five-col.dot
http://jsfiddle.net/farnuehy/17/ (Tiếng Việt)
http://blog.dongiannhat.com/2016/04/chia-5-cot-trong-bootstrap.html (Tiếng Việt)
https://blog.polarbits.co/2014/02/16/quick-tips-5-column-layout-with-twitter-bootstrap/
https://stackoverflow.com/questions/31944691/bootstrap-5-column-layout
Dropdown & Table
Bootstrap table responsive with btn dropdown-menu wrapping within table (HAY)
https://codepen.io/imarun/pen/mPjZoo (HAY HAY HAY HAY HAY)
https://www.bootply.com/YvePJTDzI0 (HAY)
Responsive Data Table
https://css-tricks.com/responsive-data-table-roundup/
http://jsfiddle.net/D2RLR/6936/ (HAY)