Excellent point, Marc. And great question. We've been exploring this issue also.
One place you which may not seem intuitive or feasible to get "do-follow" links is Facebook, in fact.
According to SEOmoz, in order to get a followed link from Facebook, simply install the page manager application, create a facebook page, install a link producing application (Ex. Simply RSS, or make your own) onto the newly created page and click publish.
Facebook pages (as opposed to profiles) are public and are crawled by the search engines. Since the link is coming from an application, it isn't necessarily no-followed.