Any professional whose work is visible on the Net will become part of the conversation that establishes reputation and creates opportunity. The blog is an active résumé that enables you to participate -- by proxy -- in that conversation.
What an active résumé should include will vary by profession and according to personal inclination. For a musician, a couple of complete tracks from each CD. For a home renovator, photos and write-ups of some completed projects -- and for extra credit, video walkthroughs. For a programmer, links to those of your applications, tools, or specifications that touch the public domain.
Here's the bottom line. What Alf calls "collaborative filtering and recommendation networks" will rival -- and my guess is, largely supplant -- conventional marketing and promotion. But if those networks can't find you, they won't be able to help you.
Jon's Radio: Active résumés
Do I really need to add anything? Perhaps a few points…
These three items will make you part of a larger community, which in turn can (will!) lead to opportunities.