One of the things I hadn't anticipated my iPhone being able to do was to act as a Yahoo! Mail notifier, but that's exactly what it does. Every time an email comes in to my Yahoo! Mail Inbox, my iPhone vibrates audibly and so I know there's an email in my Inbox (unfortunately, the Inbox is currently the only folder that Yahoo! Mail currently pushes to). The Inbox folder limitation biz notwithstanding, nice.