Data from American Advertising Federation from November 2006 shows the percentage of advertising budget that goes to emerging media according to advertising executives:
Search - 27%
Online Video - 14.9%
Blogs - 8.4%
Podcast - 8.0%
Social Networking - 7.7%
RSS - 5.5%
Mobile - 5.2%
Video Games 3.6%

Looks like there is a lot of room for growth here!