Linux Standard Base

http://www.linuxbase.org/

I don’t think I could describe the mission of the Linux Standard Base any better

than the site’s authors:

The goal of the Linux Standard Base (LSB) is to develop and promote a set of
standards that will increase compatibility among Linux distributions and enable
software applications to run on any compliant Linux system. In addition, the LSB

will help coordinate efforts to recruit software vendors to port and write
products for Linux

So far, Red Hat, Mandrake and Suse are on board and certified
as LSB compliant. Expect to see other distros join in soon. If you’re curious
about how a standard Linux distribution would take shape, the LSB could be the
clearest desciription of that will be.