On March 12th Google announced it had made significant improvements to the crawl error report and interface provided by Google webmaster tools for a site. You can see the complete announcement made in the official Google webmaster central blog here: Crawl Errors: The Next Generation.
The big improvement from my perspective is new new interface provided for errors that are reported. If you click on the url that the Google spider had a problem with, you can find out what pages linked to the problem url. And, if you fix the issue with the url, you fetch the url as Googlebot and can mark the issue as fixed. That removes the url from the list of urls reported with errors, and let's Google know you view the issue has been handled.
Personally, I've made heavy use of the Next Generation crawl error functions, and been very pleased with the new functionality. So, thought it made sense to spread the word, and also to find out what others think of the new features.
Michael