Whenever I find anything that I think is useful for me in my job I like to link it here. The links are active at the time of posting, and I try to keep it up to date:
XRM Toolbox – Probably the most important tool in my job. A set of tools that makes customisation, configuration and operations extremely simple.
Dynamics 365 Workflow Tools – An extensive set of custom workflow activities to add extra capability to CRM workflows
Ultimate Workflow Toolkit – A set of custom workflow activities to extend the capability of workflows in CRM
Notify.js – This library gives developers the ability to create nice CRM notifications on forms and views
Workflow Elements – a unique set of tools developed by CRM MVP Aiden Kaskela; I find it indispensable in coming up with creative solutions using workflows
Ribbon Workbench – now included with the XRM Toolbox, but worthy of it’s own link. This makes it really easy to add/remove commands from the CRM Command Bar, including custom buttons to call workflows, dialogs, etc.
Level Up for Dynamics CRM/365 – A really handy Chrome extension full of functions to support CRM Administrators/Power USers
Dynamics CRM Power Pane – another Chrome extension (also available on Firefox) with administrator functions to enable form manipulation and actions really easily
CRM Forum – The original CRM forum. It has since been replaced with the D365 Forum, though it is still extremely active
CRM Blogs – A list of syndicated and hosted blogs related to CRM
CRM Tip of the Day – A (mostly) daily list of CRM tips and tricks, offering valuable insights, tips and tricks to get the most out of your CRM system
Dynamics 365 Blogs – A syndicated list of Dynamics 365 blogs, YouTube feeds and Podcasts, covering a really wide range of topics
Dynamics Weekly – A curated weekly list of articles, podcasts and videos related to Dynamics 365 Customer Engagement