After some thought, here is how I currently use my Circa in my work (educational administration)...

At emory's suggestion (You ought to be on commission!), I purchased the divider tabs and clear cover for my leather notebook. I taped a business card and a picture of my wife and son to the front cover. :)

In addition, I removed a bunch of pages to "lighten the load" after adding the dividers and covers. It just seems to close better with about 15 or 20 fewer pages.

At present (subject to change in 20 minutes...), my 5 sections are as follows:

1. Home notes - I tend to keep a running log of conversations I've had, phone calls I've made etc. For example, I called about a retirement account and made a note of the date, who I spoke to, and what the resolution was. I let the days run together so when I start notes on a new day, I just write the date in the left-hand area of the page.
2. Work notes - I talk to a lot of people about a lot of stuff during the course of the day. Every day, I start a new page with the date at the top. Having one page per day is more helpful with work stuff than home stuff for me.
3. Meeting notes - If something is going to be more than a few lines of notes in my home or work section, it gets its own page here. I also use this section for classroom observations. I start a new page and call it, "Mr. Jones - Period 3 - Physics" and put the date in the little box.
4. Next Action lists - I tend to be simple. I have an @Home and an @Work and a Someday/Maybe.
5. Projects - Anything from getting ready for a staff development activity to preparing for school-wide standardized testing. If it's got a bunch of moving parts, the "stuff" goes here.

The part I'm most uncomfortable with is the Next Actions section. I used to use index cards, but I was uncomfortable with the way they got hidden away in the back of the notebook. I'm actually thinking of buying come of the Circa index cards (or a Circa punch) so I can "embed" the cards in the notebook using the rings. Curse you, Levenger, for your high-end and addictive productivity tools!!

Still to come: How to archive... I have one additional set of binder covers and 22 rings at my disposal.

All in all, I'm very happy with my purchase.

Edited to add: I just visited the link in Ironman's post above. Very interesting way to use the letter-sized Circa. That was the only concern I had with ordering the "Junior" size -- you couldn't just print-and-punch. You have to print-cut-and-punch. And even then, the Junior pages are not exactly half letter sized pages. They're close, but not exact.