I find that leveraging the most popular which are Social Media and social bookmarking works best. Linkedin generates lots of traffic as well so be sure to create a company page in linkedin. Professionals thrive in Linkedin and it's a good platform for you to get introduced to your target market. We are currently developing a Digital Collaboration Platform that incorporates both file sharing, data capture and social (www.phoenary.com) and we'll be using those sites for the soft launch next month including the sites you've listed.

Thanks!