Here are a few lessons from what the winners are doing. They might go against what you have now. Try them. You'll be surprised. 

Stop Mailing Multiple Offers in One Message

Learn from Woot.com and Groupon, and send one small email per offer. The result is a much more focused call-to-action. The response and open rate goes up accordingly. 

Personalize The Message

As best as you can, take advantage of the personalization and customization your database allows. If nothing else, use the person's first name. Personalization is a great way to build up connections between your customers and you. The more you can segment your list, the more likely people are to open and take an action. 

Use Social Sharing

My email service provider allows readers of my email newsletter to share what they've read on Facebook, Twitter, and LinkedIn (among others). This means that some of my better, more hitting newsletters get new life as links on people's Facebook walls or in their LinkedIn updates. The results are immediate. 

Offer Value, Not Just Offers

If you can, offer the occasional non-call-to-action message. Offer something of value. If you're sending out newsletters that are just uninspired clipping collections, who's going to care? What can you do to really empower your readers? That's the goal. 

Your mileage may vary, but I highly recommend that you try this, at least a few times. It's definitely something that you can work into the rest of your email marketing and then perform a/b testing on, if nothing else. What do you have to lose? Not much. To gain? A whole new view on your best asset.