I give my time here because I get so much more in return.
The main focus of my time at the moment is https://www.pixelshift.io
Useful things I've written that might help you:
blinq: a modern typescript reimplementation of linq-to-objects over iterable objects and its better typescript counterpart
BkTree: a c# implementation of a Burkhard-Keller tree for indexing data in metric spaces.
ComparerBuilder: A small c# library for easily creating complex
IComparer<T> instances that compare multiple properties. See this answer for a rationale.