Click here to read a great article by Megan Marrs which discusses multi, or cross channel marketing.
Megan talks about integrating your website, direct mail, e-mail, catalogs, retail stores, etc. into a cohesive campaign. A unified strategy is more effective in conveying your message and getting the desired response.
An interesting statistic from this article is that, "multi channel customers spend three to four times more than single-channel customers."
It is worthwhile to read the entire article to learn some strategies for utilizing multi-channel marketing in your campaign and the benefits of doing so.