It you tweet a lot and have a lot of followers, Linkbee.com is launching beta that will put ads along with a URL chopper.
It works just like TinyURL, but when you post any link, it will attach a banner ad or put an ad before the page to which you link will be displayed.
The banner ad lays over the top of the linked page. Payouts require a high volume of tweets. The most annoying part (aside from needing 4,000 banner ad displays to make $1) is the referral plans. Twitter could get real ugly if Linkbee catches on.