Scaling a Rails Application from the Bottom Up was a presentation by Jason Hoffman, CTO of Joyent. The PDF of the presentation has a mega 192 slides and touches on a ton of interesting stuff about scaling and deployment (all the way down to hash based filing).

Angels & Daemons (PDF of slides) was a presentation by Tammer Saleh of Thoughtbot, Inc that went into the details of building daemons and how to daemonize processes in Ruby. The PDF on its own is pretty useful.

Harnessing Capistrano came from Jamis Buck of 37signals. The presentation is reasonably heavy on practical knowledge and will be of use to Capistrano newcomers.

(Update: All of the presentations are now being published here. Good work O'Reilly!)