Every six months there seems to be a new, preferred way to deploy a Rails application. Mongrel+modproxy has worked OK for me for a while, but it's a bit fiddly to set up and quite tricky to make robust across reboots or crashes. Even normal restarts of my mongrel clusters sometimes fails. Now there is modrails which seems to provide most of the advantages of a mongrel cluster with the simplicity of an apache module that spawns rails processes on demand. This is definitely becoming my preferred deployment method. I might even move rentability to mod_rails when I get the chance as it'll simplify our server configuration a lot.