Sorry for the delayed response. Currently, you can call /search with different types. We don't have a direct "link" or "url" type, but you can search for all results that aren't a tweet and that will give you all results that have a link.
For example, you can enter the query "occupy -type:tweet" in topsy.com and that should give you all Twitter content with a link on the term "occupy".
Regards,
-Vanessa