LiSA

From liquid information:

No more beeps : Let your computer tell you in a real human voice when you have interesting email.

LiSA, the Liquid Information Speaking Assistant tells you who your incoming messages are from and announces them as-&-when-they-arrive, not just when you log on to check your messages. So you can hear: "You've got a message from an important client". Or maybe "You've got a reply from your lover" all with a real human voice (not synthesized speech).

How can LiSA know which messages are interesting to you? You tell her: LiSA can be customized to announce all incoming messages, announce only messages from people in your Address Book or announce messages which are only from the users Address Book unless they are replies or the words 'important' or 'urgent' are in the message Subject. You can also specify that she is to ignore emails from specified addresses all the time. She can talk a lot or a little - it's all up to you. She can even announce the time.
LiSA is perfect for anyone with a permanent Internet connection but also useful for anyone who spends some time on regular dial-up connections.