Three phone calls this week. Do Not Call Registry doesn't seem to stop these calls, because enough people aren't making complaints about them when they do. They receive a fine (if they can be traced, of course) if they are more than a blip on the complaint radar.
I am only speaking for myself, but I'm pretty sure it's Skynet, working with its barely-developed self awareness, that is making these calls. They wish to psychologically break us down, slowly over time, with phone calls, fast food and Virility... I mean Diabetes-causing soda drinks, so that we are sufficiently weakened after 15-20 years or so, for the hostile takeover.

Charity scam. Same recorded message (this number is a Louisiana origin) as (205) 265-4392 from Alabama! It's really a 'charity solicitor' who won't provide any info at all about their name, who they are working for, how much of you donation actually goes to a charity, etc...
Obviously spoofing real numbers on caller ID, because they don't want to be traced.

Non profit charity number that calls and hangs up, prompting you to call them back. A machine answers and drones on about charities, but doesn't offer any website or phone numbers to go to donate.

I receive calls this number several times a week. I don't answer it and no message is ever left on the answering machine.