Formerly called a WAP site, a mobile website is just like a regular website, but for your mobile phone. Because far less bandwidth is available to a mobile phone, and because your mobile phone screen size is only a fraction of what is on a computer, mobile sites are generally tiny compared to their larger brothers.
If you work for a billion-dollar organization perhaps your website design team can cook up something. That will be addressed at the bottom of this post - having a project team. For the rest of us who would rather outsource the work to a company that specializes in mobile website design you're in luck. Before doing anything, you need a plan - and this is it:
Determine if there is a business case for having a mobile website.