"Samba, Apache, and MySQL are probably the biggest open source
projects found on Linux (aside from the Linux kernel itself, of
course). All three have really elevated Linux for use in home
networks and corporate environments.
"With them, anyone can have a file and print server, a Web
server, or a database. All three come with pretty much every Linux
distribution you can find.
"The most ubiquitous of the three is probably Samba, because it
and the functionality it provides is found in every operating
system. Linux, OS X, the BSDs and others use Samba. It is directly
compatible with Windows because it uses the Windows file and print
sharing protocols to allow for sharing Windows file systems on
Linux and vice versa."