Here are some discussions going on regarding this update:
http://answers.yahoo.com/question/index?qid=20131206042724AA1XUZI
http://www.webmasterworld.com/google/4628292.htm
http://www.blackhatworld.com/blackhat-seo/white-hat-seo/629774-page-rank-update-today-google.html
http://www.talkarcades.com/talk-arcades/28389-google-pagerank-update-december-2013-a.html
http://www.forum.brsoftech.com/Thread-google-pagerank-update-6th-Dec-2013-6161
http://www.webmastersun.com/threads/4893-Google-has-just-updated-website-pagerank
Also See:
Google to Support Toolbar PageRank
Author Rank is the New Page Rank
Rel = “Author” – An Important Ranking Signal for Google
Free Seo Tools
Site Analysis Tools
Social Media tracking tools
OpenSiteExplorer
Backlink Watch
Seo Powersuite
New Crawl Error Alert Feature in Google Webmaster Tool
Rich Snippets in Google
Google Knowledge Graph