A quick and copy/paste you can use for Chrome and Firefox would be: (change the stuff after the # to change the color)
-moz-border-radius: 10px;
-webkit-border-radius: 10px;
-khtml-border-radius: 10px;
-border-radius: 10px;
-moz-box-shadow: 0 0 15px 5px #666;
-webkit-box-shadow: 0 0 15px 05px #666;
Matt Roberts' answer is correct for webkit browsers (safari, chrome, etc), but I thought someone out there might want a quick answer rather than be told to learn to program to make some shadows.