There is a web-based Orbiter message board where you can post general questions and suggestions. It has dedicated sections for bug reports, addon topics, and all things spaceflight.
Additional forum sites and orbiter-related pages can be found under the Forum page and the Related sites page. Another useful link for tutorials and developer resources is the OrbiterSimulator Wiki. For general information on Orbiter, see the Orbiter Wikipedia entry.
You can also join the ORBITER mailing list to exchange email with other users to get the latest hints and tricks.
Before submitting a bug report make sure you have the latest version, and that the problem is not already addressed in this FAQ or the forum.
As a last resort, you can email me directly, but I cannot guarantee that I will be able to answer all Orbiter posts.