Hello and welcome (again)
You were talking to me on Facebook in case you wonder.
Since you already got the local setup working, you are ready to start with some more advanced stuff. We can help you find areas of interest (i.e., modules you could work on) if you tell us a bit more. What do you mean by saying
add your own features to Minecraft? Is it about AI, gameplay and logic, simulation, world generation, modeling, story telling, ... (you see, there is sooo much to a game
). In case you are still undecided about these details, you could look through our wiki pages on
Google Code-in (entry level tasks, not only programming) and
Google Summer of Code (just started, many projects ideas to find there).
If you want to start with some smaller coding tasks (unrelated to a specific topic), look out for
bite-sized issues in our issue tracker on GitHub. Those are perfect to for a fresh contributor, and the issues will give you a contact person you should talk to.
Hope that helps, don't hesitate to ask more questions (preferably here or on IRC).