Those projects helped me learn a lot about Ruby. There are many but I will mention only a few of them here. Unfortunately they aren't embedded, thus they must be run in the console.
An application that intereacts with the diabolic Twitter API. It asks for a Twitter user name and shows the latest tweets mentioning that user.View on Github
An application that shows the simplest possible way to get from one square of a chessboard to another while moving like the Knight piece in the game of ChessView on Github
Tic Tac Toe
A tic-tac-toe game on the command line where two human players can play against each other and the board is displayed in between turns.View on Github