Is there any way to get a pop-up notification on my iPhone or iPad when mail arrives?
Solution 1:
With the release of iOS 5 mail can now appera as a pop up box style notifacation.
Goto Settings>Notifications>Mail> the choose "Alerts" in the alert style menu.
you will then have something that looks like a message notification when an email arrives
Solution 2:
Give BoxCar a go.
I use it in a similar way for Twitter Direct Message notifications.
Solution 3:
I use a combination of Notify and Prowl, running on a spare Mac. I found so many other uses for Prowl, such as sending push notifications from a script.