Baron Georges-Eugčne Haussmann (1852) By the mid-19th century, Paris was crowded and filthy. Emperor Napoleon III comissioned Haussman to clean it up. The ambitous Baron knocked down a bunch of old buildings to put in plumbing lines and make way for the straight, wide boulevards that define the city to this day - and, fortuitously, made it a lot easier to shoot cannons at rioters and their pesky barricades.
Derek Walker (1967) Britain's most notorious "new town" - beating off stiff competition from Crawley, Redditch and Basildon among others - was designed using a grid system borrowed from urban theorist Melvin M Webber. Webber proclaimed the virtues of "community without propinquity" (basically, "if you've got a car, who needs neighbours.") . The jury is still out on this model.
Lucio Costa and Oscar Niemeyer (1956) Before Brasília, Brazil had two coastal capitals (Rio de Janeiro and Salvador). By making a new one in the country's interior, the government hoped to populate that part of the country. Costa followed a 95-point program for the construction of rational cities written by his friend Le Corbusier, and ended up creating a city that is equally unwalkable and disjointed. Still, it takes a lovely picture.
Walter Burley Griffin (1913) Griffin, an American, won the international contest to design Australia's new capital, because his plan impacted least on the land's natural features. Work progressed slowly and in 1920 Griffin quit, convinced that his ideas were being intentionally sabotaged by bureacrats. None of the buildings he designed for the city were ever built and as late as World War II, cattle were grazing on the "lawns" of the parliament buildings.
Anshe Chung (2003) Chung is a virtual resident of the online world Second Life. Thanks to some savvy investments, she now owns an entire Second Life continent, Dreamland, that takes up 10 per cent of the e-world's land mass, and which she rents out to e-people looking for a nice quiet e-place. She then trades her Second Life dollars for, well, real ones - she's made over a million so far.