I was reading this Using Google Alerts to Build Links article and about halfway down it mentioned a great way of using alerts to keep track of who is using your articles.

By setting up a Google Alert for each of your articles you will be alerted every time Google finds a site using your article.

For the alert you could use either:

• - Your article name – if it’s unique enough.
• - Some distinctive text from your article.
• - You site name to capture all articles being used such as
    site:yoursite.com 
• - Or maybe the web address of your article such as
    www.yoursite.com/articlename.html

This could help you find out

• - not only who is using your articles
• - but how often your article is being used

which is a good way of seeing if your efforts are paying off.

Also as an added bonus

You can check out the site that is using your article.
Then if you think it may help bring you more traffic, offer them more articles or links to your website pages that may be of interest to their readers.

You can read the full set of linking strategies here Using Google Alerts to Build Links