Palouse Mindfulness is a website which offers a very extensive FREE 8-week online Mindfulness-Based Stress Reduction course.
Calm is an app that is is very useful to both people just beginning to develop personal mindfulness practices and to those who are experienced with mindfulness practices but may want to expand their skills. There is a good Free version and also a very extensive paid version available.
The app is available in a desktop version at https://www.calm.com/
The app is also available on iTunes and in the Google Play store.
