Some of the things that I actively maintain:

• JavaScript / TypeScript
  • synchronous-promise a promise-like replacement that runs synchronously, useful for testing and for providing optional sync/async interfaces for libraries
  • yafs a simplicity wrapper around common filesystem operations like reading, writing, copying and listing files
  • zarro an extensible build scaffolding built around gulp
• .NET
  • log4net: a logging framework for .NET (framework and core). Currently I'm the only maintainer for log4net and releases are quite time-consuming. If you use log4net, I'd really appreciate sponsorship.
  • NExpect: a unit-testing-framework agnostic assertions library focused on ease of readability, extension, and general use
  • PeanutButter: a suite of libraries for common functionality in .NET (framework and core), including Duck-Typing, in-place HttpServer for testing, RandomGenerators for generating all manner of random values (including for complex types, and you can guide generation) and a few more bits and bobs
  • dotnet-utils: a bunch of dotnet utilities, including asmdeps, which can show your full dependency tree for an assembly (or reverse-search for what is pulling in a dependency)
    Here are some ideas of what you can tell your potential sponsors:

Sponsorship would allow me to devote more time to these. I'm quite fortunate in that a lot of the time, extension of my own opensource packages benefits my employer or my workflow, so I can often extend my opensource packages during work hours. But sometimes there are community requests, and log4net has a backlog of issues that I rarely get to look at.