CPM Rates published by PubMatic

Source: http://pubmatic.com/adpriceindex/

• Small Web site segment: Less than 1 million page views per month.
• Medium Web site segment: Between 1 million and 100 million page views per month.
• Large Web site segment: Over 100 million page views per month.
• Aggregate Index: Data for All Web sites is computed using a weighting of 65% large Web sites, 20% medium Web sites, and 15% small Web sites based on an estimate of overall traffic in the online publishing market.

Findings

• In March '08, 76% of small Web sites saw eCPMs under $1.00, compared to 96% of medium and 94% of large Web sites
• Across all Web sites, the range of eCPMs was $0.003 to $15.25.
• eCPMs for technology and gaming sites are higher on average than other categories: $0.82 and $0.69 respectively, for March '08
• Technology eCPMs have declined by 12% from January '08 ($0.92) to March '08 ($0.82)
• eCPMs for social networking sites are among lowest by vertical, though they have increased 69% from $0.22 in January '08 to $0.37 in March '08

My take is that these numbers may be on the lower side, because PubMatic's initial set of users might be the ones, who are more stressed out with the lower CPMs in general and are thus a little more open to try out something which can monetize their traffic better than other publishers.