For those who develop fonts—professionally or otherwise—it is prudent to know where the latest and greatest documentation is located. This is useful not only when searching for specific documentation, but also to check whether there are any updates to existing documentation.
The right-side navigation bar of this blog’s landing page includes links to relevant documentation and resource pages, such as for font-related Adobe Technical Notes, the OpenType Specification (hosted on Microsoft’s website), and even AFDKO (Adobe Font Development Kit for OpenType). Also, don’t forget about the excellent font developer resources offered by Apple (Fonts), FontLab, and Microsoft (Microsoft Typography).