We have a cluster of machines and I found ssh automatic login very helpful. I also found Capistrino very helpful. Are there any other tips/tricks you found useful?
System configuration automation, such as Puppet or Chef, eases the installation and configuration documentation burden considerably. Don't just use it to install packages or anything that trivial; instead, really use the system's entire feature set to (for instance) automatically configure your monitoring system, backups, DNS server, licencing information (if relevant), and all the other anciliary gubbins that go along with bringing a machine online.