I've used apt-mirror - http://apt-mirror.sourceforge.net/ - specifically the version included with Debian in my case.

Specifiy the repositories you want in /etc/apt/mirror.list config file

Note that by default it downloads packages for the architecture it's running on (e.g. i386 or amd64 on a desktop machine) so as you'll want armel packages, start the line "deb-armel" rather than just "deb". For example, to mirror the fremantle sdk use:

deb-armel http://repository.maemo.org/ fremantle sdk/free sdk/non-free tools/free tools/non-free

[Addendum]: I'd also change "set nthreads 20" to "set nthreads 1" in the config file so it only downloads one file at a time - more considerate.