ENet for C# wraps the C-language ENet networking library. For games and other realtime applications, if you use TCP, old data can hold up newer data, even if it is no longer relevant (old positions, etc.). Your players will perceive any lost packet as a "lag burst". ENet supports multiple in-order streams of data, and allows you to decide on reliability on a per-packet basis. The library is useful for both client-server and peer-to-peer architectures.
Lhasa is a Free Software replacement for the Unix LHA tool, for decompressing .lzh (LHA/LHarc) and .lzs (LArc) archives. The backend for the tool is a library, so it can be reused for other purposes. Lhasa aims to be compatible with as many types of lzh/lzs archives as possible. It also aims to generate the same output as the (non-free) Unix LHA tool, so it will act as a drop-in free replacement.
getxbook is a collection of tools to download books from websites. There are tools to download from Google Books' "book preview", Amazon's "look inside the book", and Barnes and Noble's "book viewer". There is an optional GUI written in Tcl/Tk, and some shell scripts using OCR to create plain text or searchable PDFs and DjVu files from the downloaded books.