Nereid brought up the subject of quasar absorption lines in the "Dark Matter" post. I worked on the subject as an undergrad, so I would be happy to answer any questions you have about it. Some examples of things it tells us are 1) The power spectrum of matter in the universe (small scales). 2) The metallicity and abundances of intergalactic gas. 3) The conditions around galaxies. 4) Deuterium abundance for nucleosynthesis measurements. 5) Kinematics of gas, such as starburst outflows. Any discussion of a non-cosmological interpretation of redshift is unwelcome in this thread, as it has been thoroughly refuted in the scientific literature. Please take such things elsewhere.