These are the links that we find useful to learn PowerShell:
Powershell Blog
Central place for Powershell Community
Powershell Forums, to ask/help other fellows:
Powershell, DSC, Pester Forums
Windows Powershell Survival Guide:
https://social.technet.microsoft.com/wiki/contents/articles/183.windows-powershell-survival-guide.aspx?wt.mc_id=AID603153_QSG_BLOG_145484
Reference blogs/books by Jaap Brasser:
http://www.jaapbrasser.com/how-to-learn-powershell/
Reference list for tools open sourced as well as books/blogs: