Since the release of 1.5, WordPress has included an “update-links” program that you can call periodically to check the latest updated time of the links in your link roll. This program queries Pingomatic, which returns a list links and update times.

However, if the links in your database are of the format “http://www.timeistight.com,” the Pingomatic API won’t recognize them, even if the site pings Pingomatic religously; the Pingomatic API responds only to links without the “www,” e.g., “http://timeistight.com”.

May 31st Update: This has now been fixed. Also, Matt Mullenweg says that “Ping-O-Matic is now parsing several sources including weblogs.com for update information, so the quality of updates should be as good or better as when everyone was manually parsing changes.xml.”