I second the online calendar recommendation (there's Google Calendar for free but also a lot of others). Most of these will sync to your desktop or mobile client as well for example.
So as an example, I have my calendar online, but it syncs to my desktop (where I also have other calendars that launch automated programmed tasks like email backup while I am sleeping) and the non-automated stuff all gets synced to my phone, other laptops and tablets as well.
No matter what I am in front of, I get alarms, notifications and whatever I want (most times I don't want something obtrusive) and I sync it all through Google Calendar.
Sync is the killer feature of PIM. Google is the best free sync around at the time.