This page has been updated and quietly read about every quarter for most of the decade here, and it will continue eventually at its new digs.
These examples are what you would expect from checking search engines. With their overlap, it may not matter where to start, as you may compare excerpt endpoints between sites.
Denver Post
Washington Post
New York Times (three links included)
There are surprisingly few active foreign publication collections to compare and contrast with the American pages.
Many commercial and institutional (including self-published and subsidized) publishers embed text or pdf excerpts inside individual catalog entries, but only a few allow for one-stop linking on a collection list or search page.
HarperCollins (Australia)
HarperCollins (USA)
Penguin Books
Princeton University Press
Random House Australia
Read-It-First (St. Martins Press)
University of Chicago Press
W.F. Upjohn Institute
These following links are from inactive competitors as well as to sites that provide subsets from earlier pages or to those with eclectic, eccentric, or even unpublished selections, and concludes with author personal pages.
christianaudio (Podcast)
crosswalk.com
First Chapter
Good Reading Magazine (Subscription Required)
Hackwriters.com
OnceWritten.com
ReadersRead.com
TODAY's [NBC] Book Club
WNYC
Dan E. Moldea
Jonathan's Corner
Trong G. Nguyen (Magnification Required)
Commercial or personal submissions to Dial-A-Book and other services place chapters at many sites with browsed excerpts that can be linked later. [Try Amazon.com and O'Reilly.]
If the current list doesn't satisfy, feel free to peruse the new or archive lists from The Online Books Page or compact formatted public domain lists at Page By Page Books and Authorama. Greg Porter---GP