When I read the title I thought you made something that found the original source of a syndicated/re-posted article.

Anyway, since you have a database of submissions to HN, Reddit and Digg, there's alot of interesting things to do.

Off the top of my head, how about a side-by-side view of parallel discussions?

EDIT, some more suggestions:

Make a downloadable dump of your data at the end of each day. Would be useful for all the people scraping HN for their own purposes/websites.

Twitter would be more useful than Digg, although all the short-urls do pose a problem.

Your top15 page (http://dexjra.com/row_view) is strange. Why isn't HN there except the "First at Hacker News view" part?