CGM (Consumer-Generated Media) "encompasses the millions of consumer-generated comments, opinions and personal experiences posted in publicly available online sources on a wide range of issues, topics, products and brands. CGM is also referred to as Online Consumer Word-of-Mouth or Online Consumer Buzz. CGM originates from:

• Blogs
• Message boards and forums
• Public discussions (Usenet newsgroups)
• Discussions and forums on large email portals (Yahoo!,AOL, MSN)
• Online opinion/review sites and services
• Online feedback/complaint sites

Source: Nielsen BuzzMetrics