Given a cell number in the US (although other countries would be nice too), how to I go about figuring out the provider? Are there any web services that you know of or ETL dumps that I can use to get this information?
Ideally this component would accept a cell phone number and return a service provider.
MX Telecom looks most promising. They have an XML interface detailed here.
Another nice one (pay to get CSV file)
Here is a list of other service providers.
Before local number portability, you could determine carrier by the 3 digits after area code. This no longer works for people who "took their numbers with them" when they switched carriers.
I dont know about other countries. Here is a list of codes for Indian mobile phones. I am not aware of any webservice available. But this can stored in a DB and referred.