There is a new way for Twitter users to make money off of their accounts: Twittad. Twittad allows users to essentially "rent out" the background of their Twitter page for a fee.
Here is the breakdown of how it works for users and advertisers.
I remain skeptical on whether services like Twittad will gain popularity. The idea reminds me of the cars I see with advertisements all over them. An easy way to make money, but how many people want to sell their appearance for advertising? Not many cars on the road and probably not too many Twitter users.