KingBase is a free chess games collection, usable with most free and commercial chess programs.
Periodically new chess games are added, existing entries are revised and duplicated games are removed.
The games are mainly collected from the websites of various tournaments and TWIC archives.
KingBase is a free alternative to commercial products, but has some limitations:
No annotated games.
No games with less than 6 moves.
No games before 1990.
No games with ELO-rating < 2000.