Looking for a great way to organize your life online? MyDataBook is something I have used for a while and highly recommend. This PHP/MySQL script is free and hosted on your own server. It keeps track of your calendar, contacts, daily journal and email reminders all in a simple interface. It does take someone familiar with manual database installation as there is no auto-install available at this point. Also, if you are familiar with PHP it is very easy to customize to your liking.
Other PIMs (Personal Information Managers) can be found here.