Pure Messenger Widget is not free, but it's worth way more than the asking price. (Around a buck and change, U.S.) You can configure it to show SMS, GMail, pop email, Facebook, and/or Twitter. You can customize the look and optionally enable notifications. Even shows the contact pic, if set. It's one of those apps that has never caused me any grief, does what it's supposed to, and otherwise leaves me alone.
No relationship with the dev, beyond being a completely happy customer.