These crawls are part of an effort to archive pages as they are created and archive the pages that they refer to. That way, as the pages that are referenced are changed or taken from the web, a link to the version that was live when the page was written will be preserved.
Then the Internet Archive hopes that references to these archived pages will be put in place of a link that would be otherwise be broken, or a companion link to allow people to see what was originally intended by a page's authors.
They enable you to create your own personal dashboard. In fact, this is how I track my various projects. To enable this, new Google Code project hosting gadgets are now available for each project on Google Code. They can be discovered under the feeds link in the project homepage.