I’ve managed to keep my work outlook calendar, home outlook calendar, and mobile phone calendar all in sync using Google calendar.
Once I’d checked that my Google calendar existed (you should find that it created automatically if you have a gmail or google login), I installed the Google calendar sync application on both my home and work computers (guide here:
http://www.google.com/support/calendar/bin/answer.py?answer=89955). This runs automatically at startup, and compares your calendars every couple of hours (the frequency is configurable).
The next step was to set up an account with GooSync
http://www.goosync.com/. They use the data synchronization feature on your mobile phone (Sony W850i in my case) combined with the Google Calendar API to keep the two synchronized. There is a free basic account which I’ve used, which limits you to calendar use up to a month ahead. For a yearly fee you can also synchronise tasks and contact details. During the sign up process they send the settings automatically to your mobile phone. I then tweaked these so that the phone syncs automatically a couple of times a day.