I wrote all of the code for steemtipper minus the css which was handled by crimsonclad. As far as learning the best is just to jump in and try to build something small.
My little contribution can be found on the settings page. You used to have to upload an image somewhere and then paste the url into the settings but now you can upload just like while creating a post.
So, here is my take on the musicoin player. I don't think they would accept a pull request that added it. So if you really wanted someone to do it I would first talk to timcliff and see if he can find out if that is something steemit would even accept.
My future work falls into two buckets. @FollowBTCNews pays me for work that benefits STEEM as his way of giving back as a witness. Others pay me for projects as well and so for those I build whatever they ask as long as it isn't bad for the platform. I have turned down some offers from others for services I didn't think should exist because they were bad for steem.
The other is bucket contains my personal projects. I have a game where you can bet steem about 90 percent finished but have been to busy to get to the last ten percent although I am really hoping to soon. Another is a freelance site that I am working on when time allows. I actually looked into parsing steem blogs to rss recently and that might be revived as part of another project. If I do I will let you know. It would likely be a subscription service but it would be very cheap, maybe 1 or 2 SBD per month.