During the Sprint at the excellent Plone Tagung in Dresden I wrote a new chapter in Mastering Plone that doubles as a reference for all fields, widgets and directives in Dexterity as well as validation and default values:
Please comment here, make a pull-request or drop me a mail if you know of fields or widgets that you use and that are missing (yes, it mentions Masterselect and even has a example for Datagrid).
Thank you Philip! Good work! Volto screenshots would be indeed nice (anyone up for that task?). And bugreports regarding fields that do not work in Volto are always welcome!