A year or so ago, I discovered Topsy, which lets you plug in a URL — say, for example, for a nytimes.com graphic like our Netflix map — and see how many times people have tweeted about it and what they’re saying. It’s a great service, but its one downside is that you have to search for URLs one at a time. And sometimes you want to see how a bunch of URLs are doing relative to each other.

So, I put together a little Rails app that takes a Web site — something like the NYT home page — and looks up the first 150 or so URLs that it finds on the page using the Topsy Otter API, then displays how often they have been tweeted as an overlay on the page itself.

The app is up at twittrd.ericson.net. A few things to note:

• By default, it only looks up URLs that have a date or numeric ID in them. This is a crude way to filter down the page to just stories rather than looking up things like page nav.
• It rewrites the URLs to point to their page on Topsy, so clicking on a link will take you to the Topsy page that shows all the tweets about that URL.
• Depending upon a site’s HTML structure, the numeric overlays work better in some sites than others. nytimes.com looks reasonably close to real-life. msnbc.com does not.
• The Topsy API has a limit of 10,000 URL lookups in an hour. Since it will check up to 150 links on a URL, this means that if more than 60 or so people have been to twittrd in the last hour, I might be over my Topsy API limit. Check back the next hour to see if it’s reset itself.
• Topsy also doesn’t deal well with URLs that have the id of the story or post in the querystring, since it ignores everything after the querystring when searching. So your mileage may vary on sites with urls like post.php?id=12345.
• And it can be a bit pokey — it hits the Topsy API for each URL it finds on the page — so it can take 20 or 30 seconds to run.