Putting the meta before the actual, I just found a wiki dedicated to Against the Day, at http://pynchonwiki.com/wiki/index.php?title=Main_Page.  There's a bunch of good stuff there, I particularly like the description of the book as it appeared on Amazon, evidently written by Pynchon.
Still playing with the format, lets see what works:

Merle Rideout's Chapter (57-80)
Merle's story starts with a trip to Cleveland to join, or at least observe, an Aetherist community, a community of scientists, lunatics, and light adicts held together by their obsession and the belief in ether.  The Aetheric community begins to crumble after the capture of Charles "Blinky" Morgan, who is quite possibly some kind of living refraction of Edward Morley, of the Michelson-Morley experiment which helped to disprove the existance of Aether.  After "Blinky", a real person wanted for killing a policeman, was captured, the Michelson-Morley showed that the speed of light was constant, and no Aetheric wind was detectable.  O. D. Chandrasekhar, who was just hanging out in Cleveland at the time, puts forward that this could prove the existance of Aether, elevating it to a higher, more ubiquitous standing, making it into 'akasa', the basis of reality.  The bartender, Roswell, replies "What I worry about is that Aether will turn out to be something like God.  If we can explain everything we want without it, then why keep it?" (p63)

Merle then gains an interest in photography, becomes a lightning rod salesman, befriends a ball of lightning named Skip, and moves to Colorado to practice his photography, which is becoming closer and closer to alchemy.  In Colorado, he meets with Webb Traverse, the star of the next chapter, and they discuss politics and alchemy (p76-80).  Merle and Webb, in their very Pynchon oblique way of talking, lay out a Philosopic Mercury, or mercury without anything you'd recognize as mercury, which is a relative of the Philosopher's Stone.  To counter this, there's the 'let's call it Anti-Stone'.  If the Philosopher's Stone turns lead into gold, it seems like the Anti-Stone (Capitalist's Stone?) turns gold into explosives.  But we're in a new age, chemistry has replaced alchemy, did so around the time capitalism started to take off.  Now, instead of lead into gold we turn sweat into dollars.

Merle's path is an interesting one.  He starts directly in the Aether, and gradually descends into photography, and then almost into alchemy and mining, a complete reversal of what Plato intended.  The last lines of the chapter refer to the possibility that his life has been revolving around silver and it has been drawing him towards it.  Said like I did, it sounds like a fall for money, but Pynchon's descriptions of such falls here and throughout the book make it sound like a loving descent into ... something.

Running in parallel with Merle's story is his daughter, Dally, who is mainly pining after her mother, who ran off with a hypnotist.

Webb Traverse's Chapter (81-96)
Can't say this chapter had much for me.  This chapter is all about dynamite and freedom, starting and ending with trains being blown up on the 4th of July.  Webb is an anarchist former miner running around Colorado with his family.  Maybe this chapter is more about historical contexts that I don't have, like the Cripple Creek miner's strike.

Kitt Traverse's Chapter (97-106)
Kitt, Webb's son, goes to work for Nicolai Tesla.  If Webb's chapter was about anarchy, Kitt's is about work.  "Sure, it's always something...Chores, something." Kitt says, "Tithing." Tesla said, "giving back to the day."  Kitt even runs into Scarsdale Vibe's man, Foley (from ch2 or something), who offers him a full scholarship at a distant school in return for working for Vibe.  I'd have to go back to check Foley's story, but I believe that the tearing apart the Traverse family is the entire point of the scholarship.

Foley's own story is that Vibe, instead of fighting in the Civil War himself, he paid Foley to do it.  Foley finished the war surprisingly alive, although with a bullet in his head which allowed him to hear voices that gave him access to extremely accurate investment advice, ranging from horse races to stocks.  This link between Foley and Vibe is similar enough to the link between Morgan and Morley, Foley even says he could be more Scarsdale Vibe then Vibe himself (p102), but this repetition of doubles doesn't really have a solid shape for me just yet.

Chums of Chance's Chapter (107-118)
The Chums fly to a volcano across the world from Colorado to run unspecified tests for Dr Tesla.  It is worth noting that Tesla's work in Colorado is held by some to be a suspect in the Tunguska event of 1908.  The Chums are in a rough and divided state at the start of the chapter, as they fly to their destination, but once they go through their 4th of July experiments at the mountain, after the break they are back into cohesion.  Even Chick Counterfly wants to develop protocols to avoid this happening again (p113).

Once the experiment is complete, the Chums get more orders through the double refracting magic of a special pearl (p114).  Their next mission is to go to the North Pole via the center of the earth (Telluric Interior), to intercept a boat.  While in the Telluric Interior, they are embroiled in gnomish intrigue which is detailed in The Chums of Chance in the Bowels of the Earth.

Miles is acting odd through the chapter.  In Chicago, we saw how he was prone to bouts of extreme clarity, and we see that here as well in the adventure in the bowels of the earth.  But we're also seeing him spout just pure jibberish, like 'Gloymbroognitz'.  I can draw a parallel between Miles and Foley, but so far he seems like a plot device guiding the Chums through largely irrelevant plots.

Also, we're seeing some direct references for the ideal world of the air, and the ugly, political world of the earth, particularly the inside of the earth.

Choice Quotes

• "We were always supposed - by whom it is less clear - to be above such behavior, " asserted the "X.O." somberly.  "Literally above.  That sort of bickering may be for ground people, but it is not for us." (p113)
• "We cannot attack these fellows," protested Lindsay. "for they are shorter than we, and the Rules of Engagement clearly state--" (p117)
• "Brother, we are the stripes and solids on the pool tablke of earthly existence," the Rev explained, "and God and his angels are the sharpers who keep us ever in motion." (p86)
• The escape scene and Aetherite discussions, p61