After having a lot of speed issues with ShareThis plug-in, I've decided to digg a bit into the way social sharing works. The idea was from a post from Scott Hanselman.
Facebook URL
https://facebook.com/sharer.php?s=100&p[url]=UrlHere&p[title]=TitleHere&p[summary]=summary_here&p[images][0]=FullImageTitle
Don't forget to url encode all parameters in the query string and to use absolute urls.
You can debug the information with https://developers.facebook.com/tools/debug
Facebook meta tags
<meta property="og:title" content="...."/>
<meta property="og:type" content="..."/>
<meta property="og:url" content="...."/>
<meta property="og:image" content="..."/>
<meta property="og:site_name" content="...."/>
<meta property="fb:admins" content="...."/>
<meta property="og:description" content="....."/>
http://www.linkedin.com/shareArticle?mini=true&url={articleUrl}&title={articleTitle}&summary={articleSummary}&source={articleSource}
More details about the parameters here
https://twitter.com/intent/tweet?url=yourUrl&text=tweetText&via=TritterName
Google+
https://plus.google.com/share?url=yourUrl
http://pinterest.com/pin/create/button/?url=yourUrl&description=yourDescription&media=imageUrl
Digg
http://digg.com/submit?url=yourUrl
http://reddit.com/submit?url=yourUrl&title=yourTitle