MailServe for Leopard sets up a totally buzzword-compliant mail server on Mac OS X, the Mac Way. It sets up SMTP, UW/IMAP & POP3, and Fetchmail services, including support for SSL and SMTP authentication. MailServe can now also be configured from a non-admin account.
Mia for Gmail (was Notifier Pro for Gmail) is a desktop Gmail client which sits politely in your menu bar.
