211, at least here in Atlanta, is the number you call to if you want to find an organization to donate time or money to, or if you need help from one of these organizations.
I think that these vary in different locations. In Canada, at least, 911 is emergency, of course, 711 is Relay Services (the people that relay your message to a text device for the deaf (TTY/TDD)*, and so on), 611 is <insert phone company name> Customer Service (not mandatory), 411 is Directory Assistance, and 011 is Internationa Access Code. I think there’s a proposal to implement 311 as a Social Services Access Code, but I don’t know if or when.
I’m not sure whether any of 211, 311, 511, 611, 811 are officially assigned in Canada.
N11 codes are used to provide three digit special access services. In the US, the FCC administers N11 codes & recognizes only 211, 311, 511 & 711 as nationally assigned. Other codes have traditional uses, but whether or not your local telco uses them is up to your local telco:
211: Community information & referral service
311: Non-emergency police & other governmental services
411: Local directory assistance
511: Traffic & transportation information
611: Repair service
711: Telecommunications Relay Service
811: Business office & auto number feedback
911: Emergency
As I said, not all of them work nation wide because of the mom & pop telcos who don’t want the ILECs dictating service codes in their footprint.
Does 811 work for everybody as the “what number am I calling from” code? It does in the Northeast.