Shows how to write programs that use command-line options, read and write to pipes, access environment variables, handle interrupts, read from and write to files, create temporary files, write to system logs.
Short positive overview, explains Ruby by comparing with some other languages; focus on production; code samples, forum with many comments. [Linux Journal]
Three Ruby projects stand out (JRuby, Mongrel, Ruport) not so much for development, but for communicating well, something many projects do less well. Linux Journal.