Here are the LinkedIn groups related to Analytics, Big Data, Data Mining, and Data Science, with at least 2,000 members, ordered by the number of members. Which additional groups do you like?

All the stats are as of Mar 20, 2013. (Updated with new groups on March 25)

Group	Founded	Members	Comments last week
Advanced Business Analytics, Data Mining and Predictive Modeling	Sep 28, 2007	72,185	216
About the Big Data / Analytics / Strategy / FP&A / S&OP / Strategic Planning / Predictive & Business Analytics Group	Feb 20, 2009	54,390	133
Business Analytics	Mar 3, 2008	38,577	109
Big Data and Analytics	Mar 1, 2012	37,737	142
Data Mining, Statistics, Big Data, and Data Visualization	July 25, 2008	20,544	31
Business Intelligence & Analytics Group	Jan 6, 2008	20,000	40
Global Analytics Network	May 23, 2008	17,866	3
BIG DATA Professionals - Architects Scientists Analytics Experts	Sep 1, 2008	16,802	64
Machine Learning Connection	Mar 12, 2008	12,797	17
Actuary / Actuarial, Predictive Modeling, Data Mining, and Statistics News / Jobs / Careers Group	Sep 24, 2008	12214	0
Research Methods and Analytics	April 10, 2009	11387	17
Data Science Central	Feb 10, 2012	9,167	4
Visual Analytics	Mar 31, 2008	5704	15
Lavastorm Analytics Community Group	Apr 17, 2011	5,504	2
Predictive Analytics Network (PAN)	Mar 16, 2009	4,557	4
Data Scientists	Jun 9, 2009	3,277	2
KDnuggets Analytics and Data Mining	Feb 4, 2008 (as Decisionstats)	2,857	4
RDataMining	Aug 30, 2011	2,246	6
Healthcare Data Mining and Modeling	Jul 11, 2008	2,235	0
SAS & Data Mining	Feb 15, 2009	2,104	2

See also Top Five Big Data LinkedIn Groups, SAP blog post, Aug 14, 2012.