Twitter is definitely a great source of targeted traffic and can mean a nice chunk of change as well. Each time I think of "tweeting done right",
TwitterLit always comes to mind. (They choose a book and tweet the first sentence with a link to the Amazon page.) The creativity is astounding and inspiring. They've been featured in many prominent magazines and on many prominent websites.
If you apply a bit of creativity to your tweeting, the sky's the limit.