First And Second Life
Second Life is an massively-multiplayer online game and its constantly blurs the boundaries between real and virtual worlds. Just consider these recent articles:
Oreilly's Radar speculates that Second Life's currency could become an accepted form of micropayment on the web - even for people that never played the game: Lindens as Micropayments
Someone is suing Linden Lab (the company resonsible for Second Life) because they unfairly confiscated some of his property - worth thousands of (real!) dollars: Second Life Land Deal goes Sour
BBC is renting an island in Second Life for the online version of a music festival - happening at the same time as the real thing.