You can check ReturnPath, IBM deliverability. Marketo may still be running their benchmarking project. Or Sirius Decisions might have data. I had the link for another one, but I can't find it now.
http://blog.hubspot.com/blog/tabid/6307/bid/33288/Answers-to-Your-Top-11-Questions-About-Email-Marketing-EmailSci.aspx
http://blog.hubspot.com/blog/tabid/6307/bid/33403/The-Email-Campaign-You-Need-to-Clean-Your-List-Re-Engage-Subscribers.aspx
http://www.marketo.com/b2b-marketing-resources/category/best-practices/email-deliverability
Other services may also have data:
litmus.com
emailonacid.com
IBM Deliverability.
http://www.campaignmonitor.com/blog/post/3574/
http://www.campaignmonitor.com/resources/will-it-work/guidelines/