Search slowcore, sadcore for a huge list or the paisley underground.
Coincidentally listened to Mazzy Star atm.
David Roback and Hope Sandoval. She had a solo group called Hope Sandoval and the Warm Inventions. He had a group before called Rain Parade, he left after one album and left the band to his brother and others. He also was in Clay Allison and Opal (this being Mazzy Star essentially with a different singer, when Hope joined they changed the mood and slowed a bit down).
Jesus and Mary Chain did some collaborative stuff with them.
I have been listening to this type of music a lot as of late.
Try...
Red House Painters album on 4AD called Down Colorful Hill, if you like that try their other stuff, or their other acts with different names Sun Kil Moon or Mark Kozelek.
Codeine is great and you might like it, louder but slow and somber. Albums on Sub Pop and rereleased stuff on Numero Group records.
Bedhead, Slint, Mogwai, Low, early Cat Power, The New Year, Galaxie 500, early Yo La Tengo.
Up records group called Duster, also known as Valium Aggelein.
More contemporary try Beach House album called Bloom.
If any of these point you in the right direction let me know, and I'll go further.