Gnoptray is a mail notification utility for GNOME, that will support multiple accounts. It will sit in the notification area and display a total e-mail count. Hopefully, it will do a better job of previewing e-mail than current 'biff' like programs.
gavamail is a POP3/IMAP server implemented in JAVA for reading your gmail e-mail with your favorite mail client. Currently only POP3 is implemented but I hope to implement IMAP too. Libraries provided by the g4j and libgmail projects are used.