Where is Razor developed?
Vipul's Razor is developed and hosted on sourceforge. Here's the sourceforge project summary. It's a good idea to join the either of the razor-users or razor-announce mailing lists if you are going to run razor actively.
How can I help?
Razor's efficiency is proportional to the number of people using it. That is, more spam reports translate into fewer spams in your mailbox. If you are a Razor user, please ask your peers to use it too. If you are an ISP, you can setup a troll address (see razor-report manpage) where your users can bounce the spam they recieve, and integrate razor into your webmail system. If you are developer, you can help by contributing instructions and code to hookup razor agents with mail systems of your choice. And, finally, you can help by contributing code (see the task list for what remains to be done).