SCID - "Shane's Chess Information Database" is a huge chess toolkit with extensive database, analysis and chess-playing features.
Scid vs. PC is a usability and bug-fix fork of Scid. It has extensive interface fixes and improvements, and is fully compatible with Scid's .si4 databases. It's new features include a totally rewitten Gamelist, a Computer Tournament, and FICS, Tree and Book improvements.
Scid vs PC 4.14 download