Web PHP based Filemaker/Outlook? (Development Organization) Thread

Anyone have a suggestion for a free php program/script that works and feels like a Outlook/Filemaker of sorts? Where it has a calender view and can put important milestones, due dates, and who is responsible for each. Maybe even going as far as auto emailing people with those dates knowing they are coming up.

Im trying to make deadline organization easier for everyone involved in the mod Im on.

Thanks,

oXYnary