Has anyone ran across any good Powerpoint presentations on how to securely develop a web application in Ruby?
Peepcode has a PDF book on Rails security - it's $9 but they have a free preview. I've bought a bunch of screencasts from these folks, and they have been great.
Rory McCune is a security consultant and Rails developer who gave a presentation on this topic at Scotland on Rails. You can view the slides online. Rory blogs about the topic too.
Check out the Ruby on Rails Security Project. The offer a free book about this topic.
And of course you should read the Ruby On Rails Security Guide.
The Ruby Security book was joint developed as an OWASP project http://www.owasp.org/index.php/Category:OWASP_Ruby_on_Rails_Security_Guide_V2
It would be good to have more security related materials at OWASP
The video for Rory's Scotland on Rails presentation is also online here