I. Second Life [ http://www.secondlife.com]
Excellent reference source for all major official statistics regarding the state of the virtual economy.
II. Capital Second Life Capital Exchange [ SLcapex.com ]
A major exchange for virtual stocks in Second Life and home to several publicly traded companies. This is a great site to carry out research before investing through the forums, the prospectuses, and financial reports of every company.
III. International Currency Exchange in SL
Formerly the International Stock Exchange is now changed into a company that enables the users to trade real currencies for virtual Linden Dollars.