Google Webmaster Central offers a nice graphing feature so you can see the crawl trends but there is no way to access meaningful data. Studying crawl rate is hugely important because it helps you find out which pages are trusted most by the search engines (especially Google). The more Google trusts a page the greater the frequency it will re-visit that page. If you build a few deep links and see your crawl rate for the target page suddenly increase you can be confident that the links are highly trusted and that you should try to get some more.
