30 Minute Mandalas (30minutemandalas.com)
This combination of quieting the mind and coloring has been found helpful for those dealing with anxiety and other recovery issues. The web site offers 2-3 free mandalas to download and color, with new downloads available every month or so.

Clickncolour (clickncolour.com)
A coloring site designed for adults and older children. You can color on screen or print out the unusual designs for a calming experience.