The Google Webmaster Central blog wrote a post a bit ago about how they updated the platform so users can now see where their broken links are.
This is huge.
Do not miss this.
This means when googlebot sees a links and it leads to a dead end, you now can know about it.
This is an extremely useful tool to have. It means that you don’t need to run your own bots not to track down dead links!
To get here, go to: Webmaster Tools » Diagnostics » Web Crawl » Not Found
Here’s a quick screenshot of what it looks like:

Again, this is huge, do not miss this.