Google has created its own repositories for its linux software applications.
http://www.google.com/linuxrepositories/index.html
At the moment the only software available is Picasa and Google Desktop.
Microsoft through the Sysinternals team has released Windows Desktops, which provides Mutiple Desktops within Windows XP and Windows Vista. Sysinternals created quite a few applications and utilities for the Windows Operating System that Microsoft evntually acquired them.