You can test the current Ubuntu beta releases and submitting bug reports via Launchpad.
Or while using Ubuntu, (or Kubuntu, Edubuntu and Xubuntu) if you come across a hardware or software problem (called a bug) in the software please don't hesitate to file a bug report on it. Even if you don't know what to say, simply telling us that it doesn't work is often good enough. Here is short introduction on reporting bugs.