By using the keywords of your site and creating content or a lense on those key words. its almost like an article directory and a social bookmark site in one
Personally I like Qassia better because you can get away with shorter or already written article. Squidoo to me is for when you have a topic you want to elaborate on.
or you can use the comment module on squidoo lenses that relate to you site's content to make backlinks (nofollow)