Is there a way to do that...some kind of reverse whois or something?

Thanks.

I think whois.sc does that.
try my site on whois.sc like www.whois.sc/www.rattanpal.com
and you'll see a line
Reverse IP: Web server hosts 99 websites (reverse ip tool requires free login)

Now i am not sure if that is the number for the sites on my registrar or for the sites the web server has, where my site is hosted??