You can also download them manually (on a computer) and install the packages. If you open the .install file in a text editor, you'll see the repository url and the package name. You'll pretty much want to look here. Just find your .deb and get it. Maemo should know what to do with it
EDIT: you might want to get wireless or bluetooth internet on your pc. Manually installing has disadvantages, like not automatically finding and installing dependencies. It's much easier if you use the automated system via internet