Web Elements
Web Elements Periodic Table: Caesium
A very helpful site with a great deal of information on caesium and its properties. Very helpful. Includes an audio track of a description of this element, as well as illustrative pictures.
TED Talks
Ted: Ted Ed: Caesium or Cesium: Periodic Table of Videos
The team at Periodicvideos has created a TED-Ed Lesson for every element of the periodic table. Here are five grams of caesium in water, but did you know caesium is also used to define the length of a second? [7:17]
US Geological Survey
U.s. Geological Survey: Cesium
This site from the U.S. Geological Survey provides a nice summary of cesium from the viewpoint of a geologist or mineralogist.
US Navy
U.s. Navy: Atomic Clocks
This site from the U.S. Navy provides a great description of the history and workings of cesium based atomic clocks. Very interesting.
Chemicool
Chemicool: Cesium
Chemicool.com offers a very good summary of the key physical and chemical properties of cesium. Well organized.