Interacting with RFID receivers through serial ports is not much fun. This makes it a little better. tag-it provides a class that will monitor a serial port for you, and will dispatch events through ruby's standard "observer" functionality when a tag comes into range and leaves.

Bucaneer is a Ruby library which allows you to control your BusPirate bitbang modes (I2C, SPI, etc).

Switchy USB serial load switcher

Rubitlash is a Ruby interface with Bitlash for Arduino

RelayrAce talks to Canakit USB relay boards.

Rubitlash is a Ruby interface with Bitlash for Arduino

A Ruby port of pyFirmata, software for interfacing with firmata-enabled microcontrollers

Driver to write to Adaptive LED signs

Build a serial cable for your Zeo and interface with it with this library.