So one thing lead to another, and I ended up reinstalling Ubuntu. I had a mess of old KDE and Gnome apps that just needed cleaning up. Worse, I was installing something with apt-get, and apt-get said I had a bunch of stuff that was no longer used and could be removed with auto-remove. I checked the list, and it looked reasonable, so I ran the auto-remove. Obviously, something went wrong, because after a reboot, I had no desktop, not LXDE, nor Gnome, nor even X.
For the reinstall, I went with Xubuntu 9.04. Xubuntu provides XFCE 4 as the desktop manager. It is pretty nice, and easily customizable. I ran across a couple of minor issues, though:
1. The display manager had no idea that I have 2 monitors. Fortunately, I'd just ran across an excellent article on setting up dual monitors by hand.
2. A few of the applications had overly large fonts, in particular Evolution and OpenOffice. I mean the fonts used for the menus and interface were large. The fix is run the xfce4-settings-manager (from command line or Applications - Settings), then Appearance and Fonts. Uncheck the box about Custom DPI setting. Now all apps use the right font size.
All in all, I'm liking this as much as LXDE and Openbox. It feels lightweight, is easily configurable, and it is easy to set up a minimalist desktop.