No doubt that Twitter is one of the biggest (if not the biggest), and fastest growing social networking sites ever. Having a simple and fast way to connect is very much appreciated by Twitter users, specially these days that everybody seems to be busy and not have enough free time. But it’s not just social networking that makes Twitter popular. The fact that it has millions of users who can potentially be turned into customers, makes Twitter an ideal platform for advertisers and businesses to promote their products.
I am sure you have heard many stories of how some people are making money on Facebook, MySpace and Twitter. Let me be honest, all of these methods come down to one simple way, using your social networking account as an advertising and promotion platform. It is the one and only proven way that people are using to make money on Twitter.

Magpie  Update: Magpie is now SponsorTweets.
Magpie is a little different in the way it works. They find advertiser (in their network) who have product/service that match the topics of your tweets, and place their ads(magpie-tweet) next to your tweet. You can earn money by using different kind of ads like, Pay-per-Click, Pay-per-Sale, Pay-per-Lead and Pay-per-View. You choose if you want magpie-tweet in every tweets or one magpie-tweet  per 200 tweets.
The good thing is that they will let you pre-approve all magpie-tweets, so that you’re not showing ads you don’t want to show. Each time the ad campaign is used in your tweets, you get paid. So, basically you get paid to tweet as usual, or if you want to make more money, you can use popular keywords in your tweets that you know will get you better paying ads.