Telemarketing

Canada
Canadian Marketing Association's Do not contact list

Call your provincial telco and ask to be added to their "Telemarketing exclusion list". If they have a URL for this list, please add it here to the wiki. Typically once you've been added to the list it takes 3 months to propagate, and then you will be on the list for 3 years until you must renew.

How to annoy those annoying telemarketers
For one always have the upper hand. Put them on speaker phone so that you don't have to cramp your ear. While they talk walk into the kitchen and make yourself a milkshake, then go back and if they are still there talking then try to ask them what you missed and such. Finally after showing lots of interest and paying little attention say you weren't really interested after all. The telemarketer gets paid for the time, if you waste their time, they don't get paid.. you'll land on their do-not-call list pretty sooner than later. And you weren't even doing anything..

Making use of a speaker phone is very important in order to keep the upper hand (superior). It's human behaviour that a "Boss" or "CEO" would put you on speaker, so talk down to the telemarketer. Also it makes you more comfortable than sitting there cupping a telephone to your ear and second guessing what they may have said. When you're not even listening it protects you from the BS that may annoy you. When it's clear that the telemarketer cannot take advantage of the situation (which is what they strive for) they will usually not go further...