Alternatively, you can download
Debian packages for the armel architecture. Just search for a package, download a .deb for the armel architecture, open the .deb with something that can handle them (I think they're just tarballs; 7zip works at least), copy the data.tar file inside the .deb to the root of your Kobo, then run "tar -xvzf data.tar". You'll have to manually download all dependencies, and sometimes you have to move or link some files, but it seems to work quite nicely, in general. I'd recommend downloading packages from Debian Squeeze.
Note that doing this will rapidly fill up your root partition, though.