So after weeks of using Keith Packard’s transparent xterm, I grew tired of bugs that render the xterms nearly unusable, with streaking effects when I scroll up:

and ghosting when the application updates:

(The screenshots were captured opaque to highlight the issues; they exist with transparency too.)
Enter transparent Konsole. Debian’s KDE 3.3 packages do not enable transparency for Konsole (presumably because Debian’s X packages don’t support Composite), so I ended up rebuilding the konsole package (along with the rest of kdebase) with CFLAGS and CXXFLAGS set to -DCOMPOSITE. Transparent konsole behaves itself:

Hoary users and Debian sid users using X.org 6.8.x (from hoary or otherwise deployed) can grab my konsole package. Jorge says it works fine for him. Warning: You’ll need a Pentium III or Athlon XP or higher to use them, since they’re built with SSE floating ops. (You’ll need to run a composition manager to get the transparency effects.)