A "fact sheet" on the US Do Not Call listing is at:

http://www.fcc.gov/cgb/donotcall/

The fact sheet indicates changes from the original regulations a year or so ago including:

Telemarketers are REQUIRED to provide their telephone number to Caller ID. (In the past, most telemarketers blocked Caller ID so you couldn't call them back.)

Wireless phone numbers may now be registered. (When I signed up, only "hard wired" numbers could be registered.)

A "business specific" list is now available should you wish to block only specific businesses.

Autodialers must pick up a minimum of 97% of numbers dialed within 2 seconds of being answered.(A previous practice was to auto-dial several numbers, and ignore those who answered after an agent had someone on line. This resulted sometimes in numerous "nobody there" calls for those who didn't roost on their telephone to answer instantly.)

Registration for the basic Do Not Call list remains at:
http://www.donotcall.gov/

You may also telephone from the phone you want to register:

1-888-382-1222 or for TTY call 1-866-290-4236.

John