how to create sub site folder automatically?

Question

I have a problem, i hope that you help me to find the solutions:
I have a shopping cart to buy wines(assume url is www.winery.com). I allow user to register to create him store on my site to buy and introduce wines. when user registered successfully, he will open him site using url: www.winery.com/<registeredname>.

root url: www.winery.com
user1: www.winery.com/user1
user2: www.winery.com/user2
....
Reference: http://www.amazon.com/Target/b/103-7415064-0440659?ie=UTF8&node=1079726
(this is a store in Amazon)

How can you help me?

Thank you and best regards,
kiet vu