Because GMOD is a large and diverse collection of projects, it can frequently be difficult to find the right place to ask a question that will actually get answers. For the vast majority of GMOD projects, email is the right way to go, and for many questions, a mailing list is the best answer.
For several of the larger GMOD projects, there are mailing lists dedicated to users. These applications include GBrowse, Apollo, PubSearch, CMap and Citrina. These are subscriber-only mailing lists to cut down on spam in the list, but subscribing is easy at SourceForge page for all the above applications except Apollo, which you can subscribe at fruitfly.org site.
Many questions about Chado can be answered either by searching this website or by emailing the mailing list as well. Additionally, if the question is about how chado and another application like GBrowse and Apollo interact, it may make sense to also ask questions on those applications' mailing lists, but try to keep the schema mailing list included.
Finally, for other applications that don't have a dedicated mailing list, there are still a few options. There is a GMOD developers mailing list which is fairly low traffic but there is a good chance that you would at least get directed to the right person to ask a question. There should also be a page on this website in the GMOD_Components section of the website that should have contact information for every GMOD project.