NNDB is a C++ library that provides in-memory data storage and retrieval using syntax that is intended to feel natural for C++/STL, but which also might feel slightly like SQL if you squint and pound the top of your head with a seminal programming textbook. Columns types are fixed at compile-time and checked by the compiler.
ZXTune is a set of portable cross-platform applications (GUI/CLI) intended to play chiptunes originally created for ZX Spectrum. It features advanced ripping possibilities that let you search for music in big data sets. Supported playback formats include AY, AS0/ASC, FTC, GTR, PSC, PSG, PSM, PT1, PT2, PT3, SQT, ST1, ST3, STC, STP, TXT, TurboSound, VTX, YM, CHI, DMM, DST, PDT, SQD, STR, TF0/TFE, TFC, TFD, and COP. Supported compressed formats include CHARPRES, CC3, CC4, CC4PLUS, DSQ, ESV, GAM, GAMPLUS, HRUM, HRUST1, HRUST2, LZH1, LZH2, LZS, MSP, PACK2, PCD61, PCD62, TLZ, TLZP, TRUSH. Supported archived/container formats include FDI, HOBETA, HRIP, LHA, RAW, SCL, TD0, TRD, ZXZIP, ZIP, RAR, SNA128, and Z80.
Galera wsrep provider is a dlopenable generic replication library which implements the wsrep provider API. It provides very efficient synchronous replication, and multi-master and "parallel applying" capabilities for opaque data buffers. Its primary focus is data consistency. A transaction is either committed on every node, or not at all. It works anywhere TCP works, including on WAN, and can utilize UDP multicast where available. It is used by the MySQL-wsrep patch project to create true multi-master MySQL/InnoDB clusters.
libjmmcg is a basic, low-level library with pretensions to implementing features above and beyond (but not necessarily better than!) those implemented within the Standard C++ Library and the Boost Library. It features a library for multi-core or multi-chip SMP parallelism, a suite of hashing algorithms, functions for raising numbers to integer powers, a generic factory wrapper and a generic, multi-threaded, read-only cache (which uses PPD), arguably the world's worst sorting technique, trace output, exceptions that have the file, line, revision, function, and argument details, string utilities, logging, simple command line processing, and much more.