Since college I've had an obsession with calendars. I guess before that I was more obsessed with keeping records of things I do (chat logs, emails, whatever), and while I still keep those, I'm not as anal about them as I was before.
But calendars, I'm always trying to make mine better. I came across David Seah's compact calendar today, and I thought, wow, how elegant. My calendar has days going down the page, and hours going across, which is not intuitive at all (although of course there's nothing wrong with it; it's just uncommon). Seah's design though, preserves the Sunday-Saturday format and still shows time as one continuous line. It's on a different scale than mine too; mine is in terms of hours, whereas this is in terms of days. Consequently, while I can schedule my hourly activities very well, I sometimes lose track of days. The opposite is probably true for Seah's design.
Another interesting calendar I came across a while back is Yann le Coroller's personal information manager (PIM) design. The scope of a PIM is broader than a simple calendar, expanding to include an address book and all that. My "calendar" also serves as my to do list and birthday reminder, for example, and therefore is a limited PIM. According to Wikipedia, a PIM may also include emails (which I use Thunderbird for), journals (mix of HTML and Bash script), contact information (Gmail; I'm working on consolidating it but Gmail's stubbornly refusing to import my files correctly), news feeds (Google Reader), and even project management (I'm trying to integrate Gantt chart features into my calendar).
Anyway, le Coroller's site seem to be down right now, but I seem to remember there's a a panel which provides different information depending on what you click. Sounds really general, doesn't it. I think the appeal of his design was more in having everything in one place as opposed to the elegance shown in Seah's compact calendar.
I'm striving to do both. I smell another calendar redesign coming up...