fenneldoc Documentation validation and generation tool
Linguist syntax highlighting and language breakdown graphs library, used by Github
tree-sitter-fennel Fennel grammar for Tree-sitter, which in turns allows editors that use it (Neovim for example) to have syntax highlighting for Fennel
fennel-ls A language server for intelligent editing of the Fennel Programming Language
Neovim (It can be configured in Lua and thanks to Hotpot you can use Fennel wherever Lua is supported (which is pretty much everywhere: plugins, colors, syntax, etc.))
Spacehammer (keyboard-driven workflows for Mac OS)
Support / more resources
On Lua:
Lua mailing list - for questions about the Lua language itself or specific Lua modules (most module authors hang out there!)
Lua documentation - documentation on the Lua language, including the reference manual