Do Not Call List - U.S.
The U.S. National Do Not Call List (DNCL) is where you go to register all of your phone numbers.
The catch-22 is that this list is given to marketers - not all of whom are scrupulous. If you currently do not get marketing calls on a particular phone number (such as your cell), then I would NOT recommend registering that number on the DNCL yet. Only register phone numbers that have a problem. Also, if you still have both a home phone and a cellphone, we recommend to never give anyone your cellphone number unless you really need to. If you're filling out any kind of form or contest or whatever, give them your home phone. There is nothing worse than marketers wasting your cellphone minutes.
Realize however, that the DNCL has its limitations. Telemarketers have 31 days to take you off their calling list after you register. Any businesses that you have an existing relationship with can still call you, even if they're just trying to upsell you on a service you don't already have.
Worst of all, certain organizations are exempt from the DNCL list. Registered charities, political parties, newspapers, as well as companies conducting Surveys or Marketing Research are ALL exempt. That's a whole lotta annoying people who can still call you. I once gave old clothing to a charity and they've continued to call me every month for at least 5 years running now, despite having only given old clothes once, and despite having asked every time to quit calling me!