Apparently there is a more "correct" way to enable CPU frequency scaling in Debian 4.0 GNU/Linux Etch than I described in an older post.
For future reference:
$ echo speedstep_centrino >> /etc/modules
$ echo cpufreq_conservative >> /etc/modules
$ echo ibm_acpi >> /etc/modules
$ apt-get install cpufrequtils
Then edit /etc/defaults/cpufrequtils to read:
ENABLE="true"
GOVERNOR="conservative"