If your site has columns or events (such as a weekly podcast, a series of interviews, a monthly survey, special project) you can find a company to sponsor them individually.
This method increases the monetization options for website owner, while providing advertisers the opportunity to target more specific audiences, and reduce liabilities.
Mashable illustrates the case well. They have several options for advertising on the site, including the ability to sponsor specific columns and articles, including the “Daily Poll” and “Web 2.0 offers.
Problogger also runs group writing projects, from time to time, and before he was asked to publicly announce the project sponsors.