For those who are not in the know, a fixie, or fixed gear bicycle, is a bike with only one chainring in the front and the rear cog is welded to the rear hub. This makes for a light, simple bike that works well in flat, urban riding, but is not very practical for a lot of other riding.
The fixie trend originated originated among the urban bike messengers in major US cities as the motion and braking are applied through the pedals. The pedals are always in motion as long as the wheel is moving, just as you might find with track bikes. These make ideal trick bikes.
Unfortunately, at least in my own opinion, the trend has been taken over by "hipsters" who find a beautiful steel framed classic bike. Colnago, Pinarello, Nishiki, 3Rensho, Masi... you name it. They will then dremel off the cable and brake hangars, for a smooth frame, and then paint over the original paint in monochrome color schemes to render the bike more of a fashion accessory than a fully functional bike. In Seattle I saw more hipsters walking their fixed gear bicycles than riding them.
The saddest part is that, like most of us, these hipsters grow up to some degree or another and move on to new trends, thus rendering the bike more or less disabled.
There are a few companies out there that focus on fixed gear bikes exclusively. In Taichung IRO bikes on Zhong min South Rd. is a popular spot for fixies. I have seen a couple other shops in southern Taichung near the Art Museum, but I have not had a chance to get the addresses. I hope people who are interested in this type of riding will buy a dedicated fixie than cut up an old Nag.