I add some social widget on this blog, they are Facebook Like, Google +1(read plus one), Digg and Twitter. I use Blogger HTML/JavaScript widget with this code:
Note that I use table in this example, you can stylize it with CSS later
-On you Blogger Dashboard, go to Design, select Page Elements
-Select area where button will appear, click Add Gadget
-Select HTML/JavaScript, insert code below, then click Save
<table><tr>
<td>
<g:plusone size="tall"></g:plusone>
</td>
<td>
<a href="http://twitter.com/share" class="twitter-share-button" data-count="vertical">Tweet</a><script type="text/javascript" src="http://platform.twitter.com/widgets.js"></script>
</td>
<td>
<a class="DiggThisButton DiggMedium"></a>
</td>
<td>
<div id="fb-root"></div><script src="http://connect.facebook.net/en_US/all.js#xfbml=1"></script><fb:like href="" send="false" layout="box_count" width="60" show_faces="false" font=""></fb:like>
</td>
</tr>
</table>
Add Google +1 and Digg into <head> section:
-On your Blogger dashboard, go to Design
-Select Edit HTML
-Add this code just before </head>
<script type="text/javascript">
(function() {
var s = document.createElement('SCRIPT'), s1 = document.getElementsByTagName('SCRIPT')[0];
s.type = 'text/javascript';
s.async = true;
s.src = 'http://widgets.digg.com/buttons.js';
s1.parentNode.insertBefore(s, s1);
})();
</script>
<script type="text/javascript" src="https://apis.google.com/js/plusone.js"></script>
More info:
-Google +1 button
-Twitter Tweet button
-Digg Smart button
-Facebook Like button