"racksh (Rack::Shell) is a console for Rack based ruby web applications.. " - Marcin Kulik
"LiveConsole is a library for providing IRB over a TCP connection or a Unix Domain Socket." - pete elmore
"Wirble is a set of enhancements to Irb all included together in one easy-to-use package. " - Paul Duncan
"Sketches allows you to create and edit Ruby code from the comfort of your editor, while having it safely reloaded in IRB whenever changes to the code are saved." - Hal Brodigan
"FastRI is an alternative to the ri command-line tool (used for browsing Ruby's stdlib and third-party API docs). It is much faster, and also allows you to offer RI lookup services over DRb. FastRI is smarter than ri, and can find classes anywhere in the hierarchy without specifying the "full path". FastRI can perform full-text searching. Its RubyGems support is better than ri's, and it knows which gem a method/class definition came from." - Mauricio Fernandez