SwitchTower is a utility that can execute commands in parallel on multiple servers. It allows you to define tasks, which can include commands that are executed on the servers. You can also define roles for your servers, and then specify that certain tasks apply only to certain roles.

Manual: manuals.rubyonrails.org/read/book/17

Project: rubyforge.org/projects/switchtower

Download: rubyforge.org/frs/?group_id=1014

Install: gem install switchtower

SwitchTower 1.0 fixes several bugs and adds many new features.