I booted up the maemo ubuntu appliance to check it out and apt-mirror seems to work ok. You'll need to update the /etc/apt/mirror.list sections to change the architecture, mirror location and to add in the repositories you want to mirror.

# mirror.list config changes
set base_path /var/spool/apt-maemo
set defaultarch armel

You'll need to create apt-maemo if it doesn't exist. Copy apt-mirror for a quick start.
copy -R /var/spool/apt-mirror /var/spool/apt-maemo

# The repositories are the same format as listed earlier in this thread and in your sources.list.
deb http://scriptkiller.de/apt/ mistral main
# etc, etc.

To access them, you'll want to setup a web or ftp server to access the mirror. Then, update your sources.list on the nokia to reference the repositories.

for example, this should work (I haven't verified yet, though) assuming you're pointing apache to the /var/spool/apt-maemo directory.

http://local.workstation/mirror/scriptkiller.de/apt/ mistral main

(Using the sources.list earlier and adjusting for broken sites, there was about 650MB or so in repositories. I mirrored scriptkiller and maemo-hackers fine.)

Check out the howto linked to earlier for more details. I had it setup in just a few minutes. I hope this helps!