XLogo is a Logo interpreter written in Java. It currently supports three languages (French, English and Welsh), and is licensed under the GPL. This program is therefore free as in freedom and free as in beer. (Full license in English)
Logo is a language developed in the 70s by Seymour Papert. It is an excellent language to begin learning programming with, and teaches the basics of things like loops, tests, procedures, etc. The user is able to move an object called a “turtle” around the screen using commands as simple as forward, back, right, and so on. At each move, the turtle leaves a trail behind it, and it is therefore possible to create drawings. Operations on lists and words are also possible.
For example, forward 100 right 90 will make the turtle move 100 steps forward, and then turn the turtle 90^ to the right.
This graphical approach makes Logo an ideal language for beginners, and especially easy for children!