Google has added another feature their expanding web based programs, Google Calendar.
Gmail has been modified to automatically recognize when messages mention an event so you can seamlessly add it to your calendar.
SBC DSL had teamed up with Yahoo, and they have had a web based calendar. I never really used it much. It defiantly didn't help put appointments from emails into my calendar. I'll have to see how this goes. I would imagine for someone without a PDA or Outlook on their PC, this could be extremely useful!