Wirble is a set of enhancements for Irb.
The idea, of course, is to fill Irb with useful features without turning your ~/.irbrc file into swiss cheese. Using Wirble is simple, too. Here's what a standard Wirble-enabled ~/.irbrc looks like:
# load libraries
# start wirble (with color)
Don't like the defaults? Wirble is configurable. For documentation on enabling specific features or tweaking the color settings.