Real-time WHOIS for .COM

[Florian Weimer <fw () deneb enyo de>]

Is there some kind of real-time WHOIS for .COM (and friends) which
allows you to determine at least the corresponding registrar?  This is
helpful if you have to pull a delegation in order to mitigate a
particular threat.

Going by the name servers listed in DNS isn't particularly helpful if
it points to end-user dial-up space. 8-(