Won’t you be neighbor?

Here’s a site that does a cool reverse IP lookup to determine what domains share a particular webserver.

This can be simply amusing info (who else is sharing your site’s server), a step at trouble-shooting info (are your site’s performance problems being affected by one of your co-tenants?), or even investigative info (if you’re wondering whether the company you’re doing business with has their own server — and what other sites they have on it).