ePrompter

 

This program will check your email pop3 or web-based email (like Yahoo, AOL, Excite, Hotmail, etc) and will notify you if you have any. The interface is pretty ugly but it works great and it's free. It supports up to 16 accounts and leaves the original email on the server until you choose to delete it. It can read and send email through the original account, but it does put a small text advertisement at the bottom of the message.