For when a digital clock won’t do: analog-clock.el.
Inform Users with BoxQuote
Have a look at how to utilize the “box control” within Emacs to help users with the task at hand.
Catch elisp bugs with the compiler
Juan Garcia has a post on reducing elisp bugs using the byte-code compiler.
Emacs Lisp as a scripting language
Here is a great article about using Elisp as a scripting language.
Visualizing Lisp without parentheses
Michael Weber had the inspiration to imagine how might one visualize Lisp without parentheses in his mwe-color-box.el extension to Emacs.
Below is a screenshot from Michael’s page. More of Michael’s Emacs Hackery is available here.