Finding someone's cell phone number online can be much like looking for a needle in a haystack. This is because cell phone numbers are protected by privacy laws and cellular phone records have been restricted to privileged organizations and individuals. However these rules are changing. Recently a few cell phone number directories have opened up to the public. Now anyone can lookup cellular phone numbers without having to go through an expensive private investigator.
Looking for one of these public cell phone directories can be as difficult as finding the cell phone number itself. This is due to cellular phone directories are new. You will run into many reverse cell phone lookup sites. But these are only useful if you are investigating or verifying phone numbers.
There are also a lot of misleading and spam websites that only pretended to have the information you are looking for. These scam websites only exist to trick you to click on advertisements. Many of these ads lead to similar sites and reverse phone directories.
Another type of cell phone number directory only has someone's number if they have posted it to the site on their own. This is a highly unpractical way of finding someone's cellular number and I doubt if you would ever find a person's number unless they told you about it first.
The other site is the National Cell Phone Number Registry at http://www.cellphoneregistry.org , which is great because you can look anyone's number in US and Canada. The best part about this site is you can also search court records, criminal records and other public records most people do not even know exist about them.