As
reported by our own Gary Gibson, panmacmillan.com now offers EPUB
ebooks without DRM. I've just bought a few and I can confirm it. The download links are plain unencrypted EPUB files, not .ebx tickets for Digital Editions as provided by BooksOnBoard or Waterstone's.
They also currently offer a
3 ebooks for 2 deal for selected SF and fantasy ebooks. One of the books is Gary's
Stealing Light.
The prices could be somewhat lower and selection could be somewhat bigger, but it's still a great start.
P.S. I did not check other formats; it's possible they're DRM-free as well.