This ever-growing curated collection of interface patterns on CodePen is a reliable source of inspiration.
Thursday, May 31st, 2018
Saturday, May 17th, 2014
A lovely little selection of loading indicators powered by CSS animations and transitions.
Tuesday, April 4th, 2006
Want to indicate that something is happening on a web page, like... oh, I don't know... an Ajax request or something? Here's a cornucopia of animated progress indicators.