webdesign.tutsplus.com did a ribbon a while back, and I figured out a way to get it on using as little an image as possible. While using an image is still the most compatible way of doing it, here is a way to create a banner using in CSS3 using the code and image below. Demo is available http://jsfiddle.net/lastrose/yTVYD/

Here is the html

<div class=“ribbon”>
  <h1>3D Ribbon Effect</h1>
</div>

and here is the CSS

div{
  margin:60px auto;
  height:50px;
  width:200px;
  background-color:red;
  background-image:url(background.gif);
  position:relative;
  -webkit-border-top-right-radius:10px;
  -webkit-box-shadow:0px 2px 2px #333;
}

h1{
  line-height:50px;
  color:#fff;
  text-shadow:0px 2px rgba(0,0,0,.4);
  font-size:18px;
  font-weight:bold;
  margin-left:30px;
}

div:after{
  content: ‘’;
  background-color:darkred;
  position: absolute;
  width: 20px;
  height: 40px;
  bottom: -10px;
  right: 0px;
  z-index: -1;
  -webkit-transform: skewY(-40deg);
}

div:before{
  content: ‘’;
  width:36px;
  height:35px;
  background:red;
  background-image:url(background.gif);
  background-position:center;
  position:absolute;
  left:-18px;
  top:8px;
  z-index:1;
  -webkit-transform:rotate(45deg);
  -webkit-box-shadow:-1px 2px 2px #333;
}