I feel like I saw a site somewhere that would "dedupe" error messages commonly sent from frameworks like Django or cron errors. I cannot seem to re-find the site however. Have people heard of online tools like this that help wade through the hundreds of emails applications can possibly send at times?
Though it's not an online service, this problem can be solved by running your syslogs through tenshi.
Instead of hundreds of duplicate notifications you get what amounts to a summary of the number of times a particular event occurred over a configurable time period on particular systems.