body {
  background: #ddd;
}

#button {
  width: 100px;
  height: 100px;  
  border-bottom: 2px solid #eee;
  
  background-image: -webkit-linear-gradient(top, #999, #d0d0d0 80% );
  background-image: -moz-linear-gradient(top, #999, #d0d0d0 80% );
  background-image: -ms-linear-gradient(top, #999, #d0d0d0 80% );
  background-image: -o-linear-gradient(top, #999, #d0d0d0 80% );
  background-image: linear-gradient(top, #999, #d0d0d0 80% );
  
  -moz-border-radius: 100px;  
  -webkit-border-radius: 100px;  
  border-radius: 100px;
  
  box-shadow: inset rgba(0,0,0,0.2) 0px 5px 6px ;
  
  left: 50%;
  top: 50%;
  margin-left: -50px;
  margin-top: -50px;
  position: absolute;
}

.butt {
  position: absolute;
  width: 80px;
  height: 52px;
  left: 10px;
  top: 10px;
  cursor: pointer;
  font-family: "Lucida Sans";
  font-weight: bold;
  font-size: 23px;
  color: #888;
  text-shadow: 0px 1px 0px #fff;
  text-align: center;
  padding-top: 28px;
  
  -moz-border-radius: 100px;  
  -webkit-border-radius: 100px;  
  border-radius: 100px;  
  
  background-image: -webkit-linear-gradient(top, #eee, #bbb 70%, #9f9f9f 100% );
  background-image: -moz-linear-gradient(top, #eee, #bbb 70%, #9f9f9f 100% );
  background-image: -ms-linear-gradient(top, #eee, #bbb 70%, #9f9f9f 100% );
  background-image: -o-linear-gradient(top, #eee, #bbb 70%, #9f9f9f 100% );
  background-image: linear-gradient(top, #eee, #bbb 70%, #9f9f9f 100% );
  
  background-position: 0 6px;
  background-color: #eee;
  background-repeat: no-repeat;
  
  -webkit-box-shadow: rgba(0,0,0,.4) 0 3px 6px;  
  -moz-box-shadow: rgba(0,0,0,.4) 0 3px 6px;  
  box-shadow: rgba(0,0,0,.4) 0 3px 6px;
  
  -webkit-transition: all .1s ease-in;
  -moz-transition: all .1s ease-in;
  -ms-transition: all .1s ease-in;
  -o-transition: all .1s ease-in;
  transition: all .1s ease-in;
}

.butt:hover {
  background-position: 0 0px;
  
  -webkit-box-shadow: rgba(0,0,0,.4) 0 3px 8px;  
  -moz-box-shadow: rgba(0,0,0,.4) 0 3px 8px;  
  box-shadow: rgba(0,0,0,.4) 0 3px 8px;
}

.butt:active {
  width: 76px;
  height: 48px;
  margin: 2px 0 0 2px;   
  border-bottom: 1px solid #fff;
  font-size: 21px;
  color: #777;

  -webkit-box-shadow: inset rgba(0,0,0,.5) 0px 5px 10px;
  -moz-box-shadow: inset rgba(0,0,0,.5) 0px 5px 10px;
  box-shadow: inset rgba(0,0,0,.5) 0px 5px 10px;
}

http://css-creations.com/item/59/animated-push-button

Really Nice CSS3 Buttons I came across. Love the gradients and especially the Pushy Effects.

Amazing CSS3 Pushy Buttons (So Slick)

CSS3

CSS