I have my own web site. Through that, from time to time, I sell softwares developed by me. Another part of the site is a forum, through which I help students in Physics and Mathematics for free.
To create your own site, first decide upon a name for the domain. As an example, the domain for this site is india-forums.com
Then purchase web space and domain name from some third party. I purchased from host-monster. I find it really good. You can get the details from
http://www.host-monster.com
Then create html pages and upload into your site. There are tools available to create html pages, e.g., dreamweaver.
But, before you really jump into creating pages, decide how the pages should look like.