There are many ways to lookup cell phone numbers.  One way to lookup cell phone number is by using the website of the service provider.  The other way would be to put up a search on the search engines like Google or yahoo and get the list of sites that would offer free searches of cell phone numbers.  Not all sites offer this service for free.  A relatively new service that has been introduced now is the reverse cell phone lookup.  This allows looking out for numbers that are listed.  This cell phone directory is also opposed by certain people because of their fear towards the telemarketers.  Also, they do not want the public to access their numbers.  This would give even the personal information to the public.  This would be a great service when it comes to finding out the person who is calling.  This service is similar to the landline phone directories.