OpenProcessing.org
Processing is a great programming environment for artists. It lets you get right to the actual output that you want to work with without having to muck around with technical stuff, but also lets you control everything directly and in great detail. There are lots of procedural generation projects that have used Processing, and it’s also really handy for building prototypes.
Another reason why Processing is so useful is that its focus on spreading visual and software literacy has lead to a widespread open source community that shares techniques and code liberally.
OpenProcessing.org is just one of the places where you can find other people’s projects and look at how they work. It’s a great learning resource and a good place to check out new techniques. There are classes, both online and offline, which use the site, some of which are specifically focused on generative art. Or you can just browse the projects and get inspired.
(Be sure to credit your inspirations! Not only are the artworks licensed under CC BY-SA and GPLv2, but it’s respectful to let people know that you were influenced by them.)
While the new security restrictions on Java mean that some older sketches no longer work in the browser, they can all still be downloaded and run in Processing directly. Newer sketches can use Processing.js to output Javascript code instead of Java applets.