Just a couple small things:
Hansa is a bayesian classifier that detects programming languages based purely on the contents of a file (a reimplementation of go-enry)
It could be useful for someone implementing a pastebin, for example.
The other one is libctags, which implements reading a ctags file, which is useful for things like looking up symbols in a project or cross-referencing HTML output generated from code.
These are just building blocks for future projects I am vaguely planning, but if they are useful for someone there they are :-)