You have to do Social Bookmarking to get backlinks from those sites to your site. Stumbleupon is one such site.

Add a StumbleUpon badge to your site so your visitors can easily submit your content to StumbleUpon and you can start enjoying additional traffic from StumbleUpon users who want to see content like yours! Simply copy and paste the code into your site and start receiving free exposure on StumbleUpon.

<script src="http://www.stumbleupon.com/hostedbadge.php?s=1&r=www.yoursite.com"></script>

• Edit single.php of your WordPress theme.
• Find the following line (or similar line, depending on your theme file) in single.php or theloop.php:
  <?php the_content("<p class=serif>Read the rest of this entry</p>"); ?>
• Immediately after the line, add the code above:
• Save and upload single.php back to your WordPress theme folder. Done!

3 Ways Of Using Stumbleupon For Getting Backlinks:

1. You can "Stumbleupon" your own website by clicking on a certain page or the home page of your website.
2. Directly add your website:http://www.stumbleupon.com/url/www.yoursite.com  where "www.yoursite.com" is your site's URL
   
3. Encourage your site visitors to click the stumble upon button at the end of your post, or article.
4. The best is to get those stumbleupon subscribers with more than a few hundred followers to submit for you

For every other site that you may or may not own:

1. Install Stumbleupon toolbar first.(Done only one time.)
2. Then give thumb up for your sites or any sites you like.
3. Another page " discovery form" will open up and submit the necessary site information there.
4. Just Stumble it.