Look up any car based upon legal history, license plate, VIN, theft check, specs, and impound/towing events. Claims it's free but it really isn't. Has APIs for VIN decoding and license plate lookups.
A website that can extract many different sorts of information pertaining to IP addresses and networks, least of all querying several dozen blacklists to see if an address has been flagged as a spammer's.
Plug in the MAC address of a network card or Bluetooth device and it'll tell you who manufactured it.