You can make a ‘bookmark this’ link or button that bookmarks things straight to del.icio.us very easily with EE. Add this code wherever you would like that link to appear in your template.
<a href="http://del.icio.us/post?url={comment_url_title_auto_path}&title={title}">Del.icio.us This</a>
NOTE: You will also need to set up the comment_url_title_auto_path value inside of EE. This value is per weblog or data container, and can be set in Admin -> Weblog Management -> Edit Preferences -> and by entering the proper URL to your permalink template in “Comments Page URL”.
You can also use a popup as per this post using this code (correct spelling of “javascript” and “window”, they are intentionally mispelled as they are disallowed words in articles):
<!-- Bookmark post on Del.icio.us -->
Bookmark this on <a href="Jâvascript:void(myPop=wnidow.open('http://del.icio.us/login
/?v=2&noui=yes&jump=close&title={title}&url=
{comment_url_title_auto_path}','delicious','toolbar=no,scrollbars=no,width=700,
height=250,status=yes,resizable=yes'));myPop.focus();">Del.icio.us</a>
<!-- Bookmark post on Del.icio.us -->
Other Social Networking Sites
Here are a few other such social networking link template snippets, all of which worked the last time I checked (though you have to be logged in to each service):
<a href="http://digg.com/submit?phase=2&url;={comment_url_title_auto_path}">Digg</a>;
<a href="http://ma.gnolia.com/beta/bookmarklet/add?url={comment_url_title_auto_path}">Ma.gnolia</a>;
<a href="http://reddit.com/submit?url={comment_url_title_auto_path}&title;={blog_title} - {title}">Reddit</a>;
<a href="http://www.spurl.net/spurl.php?title={blog_title} - {title}&url;={comment_url_title_auto_path}">Spurl</a>;
<a href="http://www.newsvine.com/_wine/save?u={comment_url_title_auto_path}&h;={blog_title} - {title}">Newsvine</a>;
<a href="http://www.stumbleupon.com/submit?url={comment_url_title_auto_path}">StumbleUpon</a>