Book promotion means, in part, web site promotion. Driving traffic to your web site, and selling them on you, and proving your expertise, can be as important as that big media hit. I'm not dismissing the importance of traditional media exposure. TV and radio show appearances, and newspaper and magazine interviews are important elements of a book publicity campaign. But no book promotion campaign is complete without a focused effort on bringing visitors to your web site (and/or promoting your blog).
Arvinder Singh has written an article called Most Cost-Effective Way To Publicize Your Website that offers tips on using bylined article placements to promote your web site -- which, again, can lead to long-term book selling opportunities.