I made a post-rock compilation a few years ago and wrote out a description for it that kind of answers your questions and gives some other examples.
1. Stereolab - Metronomic Underground
from Emperor Tomato Ketchup
2. Mouse On Mars - Bib
from Iaora Tahiti
3. Mogwai - Mogwai Fear Satan
from Young Team
4. Slint - Nosferatu Man
from Spiderland
5. Tortoise - Djed
from Millions Now Living Will Never Die
6. Bark Psychosis - A Street Scene
from Hex
7. Godspeed You Black Emperor! - Antennas to Heaven
from Lift Your Skinny Fists Like Antennas to Heaven
August 2001. This is a short trip through some of my favorite albums that fall under the much maligned post-rock heading and covers the time from the beginnings of the genre in 1991 with Slint (although Talk Talk is often credited with taking rock music to this new and undefined place with their magnificent Spirit of Eden album in 1988) to the present with GYBE's 2000 release. Sometimes termed experimental rock and sometimes even called non-musical since atmospherics and free jazz elements often replace structure, most of it on this comp is fairly accessible and some of it is even quite melodic
It begins with the opening track from my favorite Stereolab album and a good dose of some driving, cool, French synth-pop. And then gets a little more playful with the electro-organic sounds of Germany's Mouse On Mars and some echoes of Kraftwerk. This is followed by Mogwai performing a 16 minute epic that builds from a quiet beginning to loud passages which then recedes back to quiet and continues to repeat almost like a swirling storm. It has become something of a blueprint for many post-rock experiments. Slint's Spiderland album is often said to be one of the defining moments in the beginning of post-rock with its angular twin guitars and long, rambling, mathematical songs and has probably been vaulted to a place higher than it truly deserves, but it's hard to minimize the far reaching effects this album seems to have had in the world of 90s experimental music. This track shows the heavier side and harder edge that characterizes some of the artists in this wide-ranging genre. One of the offshoots of Slint's demise was Tortoise, another guitar-driven, electronically-textured, experimental band from Chicago. The wonderful 21 minute Djed included here opens my favorite Tortoise album. Bark Psychosis never received much attention before the Hex album and despite much critical acclaim after its release, the long and arduous recording process drained them emotionally and financially leading to the band's demise shortly thereafter. What a testament it is then, to a band at its creative peak, taking inspiration from late-period Talk Talk and crafting some of the decade's most compelling music. The term post-rock can actually be traced to a Simon Reynolds review of this album in 1993. Godspeed You Black Emperor! is one of the more popular of today's newer bands in this wildly experimental genre. They are comprised of at least 9 musicians playing a wide variety of instruments to give their music an orchestral space rock sound. The track included here is the final of the four "movements" on their latest 2-CD set and stretches out over almost 19 minutes. Some favorites not represented include June of 44, Kreidler, Gastr del Sol (and other Jim O'Rourke projects), Low, Laika, Sigur Ros, Rachel's, Cul de Sac, Dirty Three, Labradford and many others.