How can I set up different notification tones for each of my email accounts? I have a Bionic running Android 2.3.4. I receive mail on a few accounts via the stock Email app and would like a different notification tone for each e-mail account. Can that be done?
This feature is already provided by many email apps including official Gmail app. Gmail app even allows to set different notification tone of different labels.

In Gmail, go to Settings ~> [Email-id of attached Account] (under Account Settings section) ~> Labels to Notify ~> [Label Name] ~> Ringtone (from pop-up). If your Gmail app doesn't have these settings, time to update it.

If you don't use Gmail app, specify your email app for further help. If your app doesn't provide this feature, you can't add it by your own in most of cases (unless app allows plugins). So, switch to another email client app.