[petercooper]

The Mongrel HTTP library is today the de-facto standard for running Rails applications,

No it's not. At least, not in this survey of 1100 folks who are deploying Rails apps. http://rails-hosting.com/Results/SurveySummary.html

It was the de facto standard, but Passenger has taken the baton in the last several months.

[Manfred]

Although you're probably right about Apache + Passenger becoming the de-facto for running Rails applications, I personally think that Mongrel is still ahead by a bit.

The Rails Hosting 2009 survey shows that the test group uses Passenger more, but the people in this group are not a random sampling. I would argue that people ahead of the curve are also the people who find it inviting to fill out such a survey.