My son is enthusiastically programming simple games in Scratch. However Scratch is a very simple programming environment (no subroutines even), and I can see that soon he is going to need to move on to something else.
Does anyone know of a good learning language that makes graphics easy but provides "real" programming features like data structures, functions, arrays and lists?
Bonus points if it runs under Linux (Ubuntu). An answer of the form "language Foo with library Bar" is also an option.
How about lua?
There is nice graphic "engine" called LOVE which is fully programmable in lua. It has nice documentation and it's not very hard.
There are also several other similar engines using lua:
There was another 2d engine, but I can't find it at the moment, it was similar to LOVE, but with a little different approach to things.
I would recommend LOVE for starters as it's very easy, has nice tutorials and most importantly you can do nice stuff right away.
Also lua is commonly used as game scripting language. For example all addons for World of Warcraft are written in lua, in fact all of the interface is written in lua. It means that it's very easy to find answers to game related questions in lua. Also if you happen to own a game which uses lua as scripting language, you could easily add your own stuff to it.
I wrote this from game perspective, but there are quite a lot projects which use lua as scripting language.
You could also try python, but it doesn't have so good out of the box, ready to use and easy to learn/understand tools.
Also here's a link to lua manual.