Thanks for the ideas! I'd prefer something smaller than a backpack or briefcase. The bags like Grindergear and Rhinopak look pretty cool, but I worry that the "box" shape may be inconvenient to carry every day, and I don't like waist packs.
Bluecken's suggestion of the Roadwired case is closer to what I'm looking for - flat (like a notebook computer) to fit in a briefcase for those situations but small enough to carry around comfortably with a book or pad of paper. I looked at Roadwired's site, and came up with the following that looks reasonably professional and roomy enough for my stuff:
http://www.roadwired.com/store/Produ...2&Productid=28
However, it doesn't look like it has a lot of pockets for flash accessories. I'll have to check it out at a store. I'm also debating going a little larger like v8sho suggested and getting a shoulder-strap camera bag to hold the accessories and my camera.