To learn & practice hacking we have to setup our lab environment because hacking real sites is a crime. Setting up a lab environment requires a lot of effort and time. To overcome all these problems OWASP has initiated Broken Web Application Project.
Owaspbwa Project is a collection of vulnerable web applications that is distributed on a Virtual Machine in VMware format. Download this Vmware from – http://code.google.com/p/owaspbwa/wiki/Downloads and open it with VMPlayer. Now type Owaspbwa vm IP from any browser and start practicing your hacking skills.
To practice hacking on a .NET website follow this article- http://www.securitylearn.net/2011/07/16/hackmebank-on-windows-xp/