Software to Block Unwanted Calls

http://blogs.zdnet.com/ip-telephony/?p=888


Caller ID Manager can:

-Block anonymous and unidentified numbers, while allowing all others;
-Block up to 175 numbers, area codes or prefixes, or;
-Allow only callers you 'Invite' by name, number, or 'Wildcard' to ring your phone, and block others as you choose

http://www.privacycorps.com/products/?id=20