I\'ve used straight Mongrel, I\'ve used Mongrel clusters behind Apache, I\'ve looked at Thin, and I\'m becoming very intrigued by Passenger. I\'ve looked at Nginx, too. I\'ve lo
Capistrano + Deprec for actually setting up my stack on Ubuntu and physically managing the deployment.
Nginx proxying to Mongrel clusers for the server architecture. It isn't the newest, bleeding edge technique but it works well, it is getting well-documented, and it is very, very high performance even when working on small VPSes. Assuming you haven't borked the application you can Slashdot a 128 MB Slicehost VPS and it just keeps coming back for more.
Having said that: there were a lot of gotchas the first time around, until I figured out how Nginx actually worked. After that its amazing -- like a little Apachelet with a slight Russian accent.