I decided to take part upon developing Ubuntu applications although I am having trouble finding projects to contribute in C, C++, C# and Java at Launchpad (not necessarily Launchpad alone). Can you offer several projects that are Ubuntu related?
You may want to take a look at OpenHatch.
While not directly affiliated with Ubuntu or Canonical, OpenHatch has project listing of a number of upstream projects (Django, LibreOffice, Rhythmbox, for example) in a variety of languages and difficulty that have the potential to improve Ubuntu.
For the beginning developers, the site also has a number of basic tutorials 'missions' aimed at getting the budding developer familiar with using dev tools such at git, diff, and patch.
A quick search on 'Ubuntu' shows a number of projects available that directly relate to Ubuntu such as writing test cases or working on a bug in Evince.
Disclaimer: I've had the OpenHatch site linked in my user profile for some time, but I am no way affiliated with them other then being a member on their site. Hope this helps in getting you pointed in the right direction.