Ask not what Octave can do for you, ask what you can do for Octave!
There are a number of ways that you can contribute to help make Octave a better system. Perhaps the most important way to contribute is to write high-quality code for solving new problems, and to make your code freely available for others to use. For inspiration, we have a wish-list of projects and feature requests.
If you have modifications to the core Octave distribution (bug fixes or enhancements), please post the changes to the http://bug@octave.org mailing list.
If you've written a useful function for Octave that you would like to make available for others to use, please consider contributing it to the Octave Forge project http://octave.sf.net.
If you find Octave useful, consider providing additional funding to continue its development. Even a modest amount of additional funding could make a significant difference in the amount of time that its author can devote to development and support.
If you cannot provide funding or contribute code, you can still help make Octave better and more reliable by reporting any bugs you find and by offering suggestions for ways to improve Octave. But before sending a bug report, please read the bug reporting guidelines so that you'll know what information is useful to include in your report.