I think I officially have too many notebooks going at once right now. Currently:
1. A large Moleskine that is my current journal. I like these - they lay absolutely flat when open (no writing up to and away from a hump), the covers are stiff enough to allow for writing without a table nearby, the pocket is handy for interesting receipts and ticket stubs and whatever other little souvenirs I care to put in there, the elastic keeps everything tidy, and the ribbon means I don't have to hunt for my last entry. Downsides: they're ridiculously expensive, for one! I have a batch right now that I got from someone on a message board, and therefore didn't pay all that much for 'em...when those are gone, we'll see if I keep using them. Other downside is that the paper isn't altogether fountain pen friendly. There's bleed-through using anything but a fine pen, and even with a fine pen some inks don't work. And feathering occurs pretty much no matter what.
2. The large Rhodia A4 sized notebook I just started for story writing. I <3 Rhodia paper. Loooove. It's a tiny bit thinner and maybe not quite so slick as the other gold standard for fountain pens: Clairefontaine. I've used both, and I'm not sure I have a definite preference, but the Rhodia pads are cheaper and more readily available, and are easier to find in graph format, which I like...
3. An Ampad Gold Fibre notepad at work, used for meeting notes, tracking my time, taking notes on tasks and procedures so I can remember 'em, etc. It's my memory. Can't function without it.
4. A logbook I've been keeping in addition to the journal. It just has a brief rundown for each day, to help me remember when I did stuff: "Ordered still more Rhodia paper from Swisher Pens. Made stuffed peppers for dinner - not as good as recipe A. Started reading Jane Eyre again." That sort of stuff. It's a good quick reference. My journal has a lot more thoughts and complaints and other fluff...
5. The mini Moleskine I keep in my purse or coat pocket, and use for story ideas for future stories, current-story brainstorming, current-story notes for easy reference (things like time lines, minor character names, scenes-to-be-written).
6. A mini memopad for reminders, grocery lists, to-do lists for home. I used to use sticky notes, but this is tidier, and I can refer back to earlier lists more easily.
7. A mini Rhodia pad for pocket-carry - for poems, mostly.
8. A tiny Japanese notebook I got when visiting my brother in San Francisco, used for fountain pen ink scribbles and comparisons, so I can remember what a particular one looked like with a particular pen or in comparison with similar colors.
I *think* that's about it. It's a lot. I could probably combine 5 & 7, I suppose, but they do all serve their purposes. Legion though they be, they get used. It makes me feel a *tiny* bit less guilty about all the additional notebooks waiting in the wings. I'm a compulsive paper buyer. I can't help myself. I love papery goodness...