Ask HN: In what interesting ways do you parse emails for your web app?

You might be familiar with TripIt's email parsing feature. Basically, you forward trip itineraries and airfare/hotel booking confirmations to TripIt, and it imports it into TripIt for you. It made TripIt so much more useful and convenient.

Now I am working on a hosted email parsing service and I want to present data in a more useful format to web app developers. I started simple, extracting URLs and phone numbers from the email.

So I want to ask you, in what interesting ways do you parse emails for your web app? Or do you have any novel ideas?

Shameless plug: http://www.apinbox.com/ It's a free way to get incoming emails for your web app.