Hi there :)
My client currently has a site at (his targeted keyword).com and also owns several domain names that are variations of his search terms, onto which I've published articles to link back to his site... perhaps iffy but the articles themselves stand up to scrutiny and provide genuine value themselves even if they really exist to create links ;)
I am thinking of employing for lack of a better term a rolling 301 strategy with these extra domains.
Basically, I would periodically publish new articles to each domain, and some time after they'd been indexed, move them to the client's main domain and 301 the page from the outpost domain. This would simply be ongoing, there would always be new articles published to the domains, with each eventually being rolled and 301'd into the main site.