Calendar Software

I am searching for a calendar system that will support:

1. Access to the calendar from my local system
2. Access to the calendar via the Internet
3. Provide multi-user support so we may share calendars via the Internet
4. Preferably would sync with Google, Outlook, and/or PDA
5. Preferably low cost as this is for a company of less than 10 employees

I have come across a product call Cozi Central and it handles 1,2,3,and 5, and though that might be close enough, it is family oriented, not business oriented. I cannot believe there is nothing out there!?!?!?!?