Steve Rubel spotted a feature recently added to Google's real-time search engine. If you Google a popular query and go to the "updates" section, you'll see see a list of web pages frequently linked from messages posted on services like Twitter, Google Buzz, FriendFeed etc. Try one of the hot topics from Google Trends and you'll certainly get a list of popular links.
There's also a way to find all the messages that link to a web page using the link: operator. Here's a list of messages that link to the New York Times website. Google will certainly add feeds for real-time search results and you'll be able to monitor all the links to your sites.