Hello, I've started a company, messagingreminder.com, that automatically sends your calendar appointments to your mobile phone.
The service was started because I was constantly forgetting about my various commitments. And although PDA's are great, they aren't practical to carry around everywhere -- but you always (for the most part) have your mobile phone with you.
The service is very easy to use: download and install the client software that synchronizes your calendar with my service. Once you have synchronized your calendar, you can try off your computer, which you can't do with other similar services and tools. And, finally, the service will send a reminder to your mobile phone before your appointment.
It's a great service at a great value, so I encourage you to try it out free for a month.