The latest version of my Ear Trainer includes random melody generation! This new feature is a great way to strengthen your ability to play by ear. See the updated "exercises" section for more details.
I have several additions and improvements in mind for future versions, but with this recent version I'm finally pleased with its overall feature set.
I should also mention that it is only *lightly* tested at this point. While there are some oddities that I do know about, I think it should be fairly stable. If you happen to find something that simply doesn't work, please let me know.