zTabs is a jQuery plug-in written by Zurka Interactive. It makes hierarchical tabbed user interface for programmers. We've used it on numerous projects over the years. It's been updated and improved at various stages. Along the way other people have asked to use it so we decided to make it open source.
Please feel free to use the contact form for questions or comments about zTabs. Zurka can also provide professional support for organizations using zTabs or interested in developing their own jQuery plug-ins.