second life 
There are a range of articles and resources here that talk about Second Life. This should help you get a feel for what is going on.
SL and Business
A quick overview on our sister-site SL Tourguides
”the application that turns social software into mainstream media”
Bret Treasure
The blog of Inside This World founder Bret Treasure. Discusses the business potential of Second Life and the entry of real life businesses.
“the difference between this and a web site is the level of involvement”
Irving Wladawsky-Berger
IBM’s Vice President of Technical Strategy and Innovation on virtual meetings, e-commerce, using Second Life in business.
“will not only transform IT but business itself”.
Robert Scoble
Former Microsoft technical evangelist discusses Second Life as a new operating system
“I think Microsoft needs to pay deep attention”
New York Times
Article titled “a virtual world but real money”. Overview of corporations in Second Life.
“fast becoming a three-dimensional test bed for corporate marketers”
Fortune
Senior Editor David Kirkpatrick on Second Life's significance
“We're seeing something new and important.”
Text 100
Global PR firm blogs about their view of Second Life
“offers interesting new possibilities for education, innovation, collaboration and marketing”
New World Notes
Authoritative, detailed and highly readable blog on all matters in Second Life.
“a world that's tripled in population within a few months”
Wikipedia
Again, comprehensive detail. Includes a list of businesses active within Second Life.
“a user-defined world of general use in which people can interact, play, do business, and otherwise communicate”
Download it here