You'd be surprised. Tor and Solaris both offer DRM free books on Amazon. Also anything self published tends to be DRM free.
I saw the writing on the wall and downloaded my books from Amazon a few months before their announcement. Out of around 1000 books I had 300ish that were DRM free.
Dumb question, but: is there a way to find/filter ones that are? (I can't seem to find anything in the (web) UI that makes it clear which books are downloadable.)
I have some tor books, but I used to download them as .azw even though they had the "this book is drm free ..." blurb at the beginning. (was back before amazon stopped downloads)
Now they could actually be distributed as unencrypted .epub